The present invention relates to the field of polymer chemistry. In particular the invention relates to a process for the preparation of polymers from at least a vinyl halide monomer, such as vinyl chloride, and at least another polymerizable monomer that contains only one ethylenic double bond by free radical polymerization in aqueous medium, and to the polymer obtained therefrom.

BACKGROUND ART

Polyvinyl halides), in particular polyvinyl chloride) (PVC), are among the largest volume thermoplastics in the world due to its great versatility and its excellent price/performance ratio that make the PVC compounds to be used in rigid and in flexible applications.

In rigid applications, to reach high impact values required for some end uses, it is necessary to incorporate impact modifiers in the blending step, which increases the cost of compound formulations.

US20090143547 discloses a process comprising the copolymerization or graft-polymerization of a) 90.0 wt% to 99.9 wt% based on the total composition of vinyl halide monomer or a monomer mixture including vinyl halides, and b) 10.0 wt% to 0.1 wt% based on the total composition of alkyl esters of alkyl acrylic acid monomers or the acrylate polymer latex/powder, wherein the former can be added stepwisely or all in one time and the later can be charged continuously into the reactor during polymerization or charged into a reactor before polymerization. Particularly, as it is understood in the mentioned patent application, the alkyl esters of alkyl acrylic acid include methacrylates. More particularly, Example 2 discloses the reaction of a mixture of methyl methacrylate and butyl acrylate with vinyl chloride monomer in the presence of a free radical initiator in aqueous suspension. US41 18440 involves the polymerization in aqueous suspension of ninety parts of vinyl chloride and ten parts of allyl methacrylate in the presence of a free radical initiator to obtain a crosslinked product. The goal of this cross- linked polymer is to provide fire retardancy to the product.

WO 2013014158 discloses a process to synthesize random copolymers of vinyl halides and acrylate monomers by a reversible-deactivation radical polymerization. However, a long process is required and it involves the use of expensive reactants. The copolymers obtained have low thermal stability that limits their applicability and a high tendency to agglomerate that difficult their handling. CN 101386661 discloses a process in which a highly branched polymers using a mixture of chain extender (e.g. diallyl fumarate) and chain transfer agent (e.g. dodecyl mercaptant) to achieve high degrees of polymerization (2400-2600). These products have relatively low apparent density (0.400- 0.420 g/cm ³ ), that limits significantly the productivity in processing steps. Thus, there continues to be a need of providing polymers made from vinyl halide monomers and a second monomer with improved impact properties even at low temperatures without incorporating of impact modifier to the compound formulation, with improved fusion behaviour and processability without incorporating processing aids or internal lubricants, and providing an increased productivity while maintaining the thermal resistance.

SUMMARY OF THE INVENTION

Inventors have developed a new process for the preparation of range of polymers from vinyl halide monomers (monomer A) and at least one monomer B either by redox or thermal free radical polymerization in aqueous medium.

Advantageously and surprisingly, the process of the invention allows obtaining a range of polymers based on vinyl halide monomers, having enhanced apparent density and impact strength, while maintaining the thermal properties required for rigid applications. Particularly, the unexpectedly high apparent density leads to a higher productivity during processing the dry-blend to obtain pellets or final products, as it is done habitually in PVC, because the higher apparent density allows processing a higher mass of product per unit time.

Unlike the polymers of the invention, the polymers disclosed in the prior art do not provide such high apparent densities. Particularly, in comparative example 2 below, reproducing Example 2 of US20090143547, the apparent density of the obtained polymer comprising methyl methacrylate was 0,1 10 g/cm ³ , significantly lower than the one of the polymers of the invention. As it is shown in Comparative Example 2 disclosed herein, the conditions used in Example 2 of US20090143547 lead to a very low conversion. Conversion can be increased by using higher amounts of initiator (see Comparative Example 3 below), but the apparent density remains low. In addition to this, this range of polymers has good mechanical properties, such as good tensile properties, presenting high tensile strength values, and maintaining the required elongation at break. These properties lead to an increase of the toughness and impact properties of the products. Besides, surprisingly, the obtained polymers have good handling and processing properties and a good drying behaviour, being possible to reach in the drying step the same temperatures than the ones used in conventional PVC resins. In addition, the performance of the products during storage is also maintained.

Thus, an aspect of the invention is the provision of a process for the preparation of a polymer from at least one monomer A which is a vinyl halide monomer and at least one monomer B that contains only one ethylenic double bond either by redox or thermal free radical polymerization in aqueous medium, wherein the at least one monomer B is present in the polymer in an amount of up to 25 wt% of the total monomers in the polymer, being the sum of the at least one monomer B and the at least one vinyl halide monomer in the polymer of 100 wt%, the process comprising the following steps: a) mixing water, at least one amphiphilic substance, and optionally a buffer, a specific amount of the at least one monomer B, and a specific amount of the at least one monomer A at an appropriate temperature to carry out the polymerization, wherein the amount of the at least one monomer B is from 30 to 100 wt% of the total amount of monomer B and the amount of the at least one monomer A is of from 10 to 100 wt% of the total amount of monomer A; adding either a redox or a thermal initiator in order to start polymerization and allowing the system to react until reaching a conversion from 10 to 99 mol% of monomers; provided that when the amount of any of the monomer B or of the monomer A in step a) is less than 100 wt%, the process comprises a step b) adding in one or more steps the remaining amount of monomer A and the remaining amount of monomer B, optionally, an additional amount of the amphiphilic substance, optionally, an additional amount of the initiator, and optionally, a buffer, and allowing the mixture to react; wherein once finished the polymerization reaction of step a) or of step b), the conversion of the monomers is higher than 70%; provided that monomer B is other than a methacrylate monomer. Another aspect of the invention relates to the polymer obtainable by the process of the invention.

The invention also concerns any article of manufacture made of the polymer of the invention.

The article can be manufactured by a process comprising forming said article from a product obtainable by the process of the invention. The article can be obtained by methods known in the art, such as by extrusion. BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 depicts the fusion curves of the products obtained in Comparative Example 1 (continuous line) and in Example 1 1 (dashed line). Fig. 2 depicts the DMTA diagrams carried out on products obtained by Comparative Example 6 and by Example 8.

Fig. 3 depicts the result of the TGAs carried out on products obtained by Comparative Example 6 and by Example 8.

Fig. 4 depicts the results of static thermal stability of products of Example 8 and of Comparative Example 6. The samples were heated in in a Werner- Mathis oven at 180°C and withdrawn therefrom at regular intervals of 10 minutes during 70 minutes.

Fig. 5 shows the GPC curves obtained of products of Example 8 and of Comparative Example 6. DETAILED DESCRIPTION OF THE INVENTION

The term "ester" is represented by the formula -OC(O)R ¹ , where R ¹ can be an alkyl, alkenyl, alkynyl, aryl, aralkyi, cycloalkyi, or heterocycloalkyi group, as defined below.

The term "alkyl", as used herein, means a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n- butyl, isobutyl, t-butyl, pentyl, hexyl, heptyl, octyl, ethylhexyl, decyl, dodecyl, tetradecyl, hexadecyl, eicosyl, and tetracosyl. A "lower alkyl" group is a saturated branched or unbranched hydrocarbon having from 1 to 12 carbon atoms. In one embodiment, the alkyl group has 1 to 8 carbon atoms.

The term "alkenyl", as used herein, means a hydrocarbon group of 2 to 24 carbon atoms and structural formula containing at least one carbon-carbon double bond. In one embodiment, the alkenyl group has 1 to 8 carbon atoms. The term "alkynyl", as used herein, means a hydrocarbon group of 2 to 24 carbon atoms and a structural formula containing at least one carbon-carbon triple bond. In one embodiment, the alkynyl group has 1 to 8 carbon atoms.

The term "aryl", as used herein, means any carbon-based aromatic group including, but not limited to, benzene, naphthalene, etc. The term "aromatic" also includes "heteroaryl" which is defined as an aromatic group that has at least one heteroatom incorporated within the ring of the aromatic group.

Examples of heteroatoms include, but are not limited to, nitrogen, oxygen, sulfur, and phosphorous. The aryl group can be substituted with one or more groups including, but not limited to, alkyl, alkynyl, alkenyl, aryl, halide, nitro, amino, ester, ketone, aldehyde, hydroxy, carboxylic acid, or alkoxy, or the aryl group can be unsubstituted.

The term "aralkyi", as used herein, means an aryl group having an alkyl group, as defined above, attached to the aryl group. An example of an aralkyi group is a benzyl group. The term "cycloalkyi", as used herein, means a non-aromatic carbon-based ring composed of at least three carbon atoms. Examples of cycloalkyi groups include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, etc. The term "heterocycloalkyl", as used herein, means a cycloalkyi group as defined above where at least one of the carbon atoms of the ring is substituted with a heteroatom such as, but not limited to, nitrogen, oxygen, sulfur, or phosphorous.

The term "acrylate", as used herein, refers to esters of acrylic acid. Polymerization of acrylate monomers yields acrylate polymers. The term "alkyl acrylate", as used herein, refers to esters of alkyl acrylic acid. As shown in the Scheme I below, methacrylic acid and ethacrylic acid are examples of alkyl acrylic acids, and methyl methacrylate, butyl methacrylate and methyl ethacrylate are examples of esters of alkyl acrylic acid. Esters of methacrylic acid form methacrylate polymers upon polymerization.

Scheme I. Acrylic acids and examples of alkyl acrylic acids and of alkyl acrylates

R ² O

H,C=C— C— O— R ¹

R ¹ , R ² = H, acrylic acid

R ¹ = H, R ² = C _n H _2n+ i , alkyl acrylic acid

n=1 , methacrylic acid

R ¹ = alkyl, R ² = H acrylate

R ¹ = alkyl, R ² = C _n H _2n+ i alkyl acrylate

n=1 , methacrylate

n=2, ethacrylate

As an instance, in the scheme above, n is an integer from 1 to 10.

The term "aqueous medium" as used herein designates water alone or a mixture of water and a water-soluble organic solvent. Examples of the water- soluble organic solvent to be used in the present invention are those organic solvents which are miscible with water at normal temperature such as methanol, ethanol, n-propanol, iso-propanol, tert-butanol, Cellosolve, methyl Cellosolve, butyl Cellosolve, methoxy butanol, carbitol, methyl carbitol, acetone, dioxane, methyl Cellosolve acetate, carbitol acetate and diacetone alcohol, and those organic solvents which are miscible with water to a certain extent at normal temperature such as n-butanol, iso-butanol, sec-butanol, methyl ethyl ketone, methyl acetate, ethyl acetate, and Cellosolve acetate. The term degree of polymerization" (DP), as used herein, refers to the number of monomeric units in the polymer chain. The degree of polymerization is given by the following formula:

DP = M _n /Mo where M _n is the number average molecular weight determined by Gel Permetation Chromatography (as explained in the Examples section) and M ₀ is the molecular weight of the monomer units. All percentages used herein are by weight of the total composition, unless otherwise designated.

As mentioned above, an aspect of the invention relates to a process for the preparation of a polymer from at least one vinyl halide monomer (monomer A) and at least a monomer B that contains only one ethylenic double bond either by redox or thermal initiated free radical polymerization in aqueous medium under the specific reaction conditions mentioned above.

In another particular embodiment, optionally in combination with one or more features of the particular embodiments defined above and below, the obtained polymer has a degree of polymerization from 100 to 2200, particularly from 200 to 2000, more particularly from 400 to 1800.

In another particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the obtained polymer has an apparent density higher than 600 g/cm ³ , particularly from 600 to 800 g/cm ³ . Unlike other processes of the prior art, the process of the invention allows obtaining polymers with a low percentage of the at least one monomer B that present particularly high apparent density and improved impact strength that can be used advantageously for rigid applications. Additionally to the improved impact properties of the products, other mechanical properties of interest such as elongation at break are maintained, and so there is no need to incorporate impact modifiers to the polymer. Moreover, the polymers obtained by the process of the invention have an improved fusion behaviour and processability without incorporating processing aids or internal lubricants, and they provide an increased productivity while maintaining the thermal resistance.

The process of the invention is advantageous because it can even be carried out in only one stage, which allows using a single reactor and reducing the time needed to obtain the final polymer.

In a particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the invention relates to a process for the preparation of a polymer from at least one monomer A which is a vinyl halide monomer and at least one monomer B that contains only one ethylenic double bond either by redox or thermal free radical polymerization in aqueous medium, wherein the at least one monomer B is present in the polymer in an amount of up to 25 wt% of the total monomers in the polymer, being the sum of the at least one monomer B and the at least one vinyl halide monomer in the polymer of 100 wt%, the process consisting of the following steps: a) mixing water, at least one amphiphilic substance, and optionally a buffer, a specific amount of the at least one monomer B, and a specific amount of the the at least one monomer A at an appropriate temperature to carry out the polymerization; wherein the amount of the at least one monomer B is from 30 to 100 wt% of the total amount of monomer B and the amount of the at least one monomer A is of from 10 to 100 wt% of the total amount of monomer A; and adding either a redox or a thermal initiator in order to start polymerization and allowing the system to react until reaching a conversion from 10 to 99 mol% of monomers; provided that when the amount of any of the monomer B or of the monomer A in step a) is less than 100 wt%, the process comprises: b) adding the remaining amount of monomer A and the remaining amount of monomer B, optionally, an additional amount of the amphiphilic substance, optionally, an additional amount of the initiator, and optionally, a buffer, and allowing the mixture to react; wherein once finished the polymerization reaction of step a) or of step b), the conversion of the monomers is higher than 70%, provided that monomer B is other than a methacrylate monomer.

In the process of the invention the at least one monomer B is present in the final product in an amount up to 25 wt% providing an unexpectedly high apparent density and impact strength. In a particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the amount of monomer B in the polymer of the invention is from 3 to 25 wt%. When the ratio of the at least one vinyl halide monomer A to the at least another monomer B in wt% in the final product is from 97/3 to 90/10 the polymer has an unexpectedly high apparent density, which results in a particularly high increased productivity during processing because the higher density allows processing a higher mass of product per unit time. An additional advantage is that the fusion behaviour is improved and enhanced impact properties in the final goods are obtained with these resins. Accordingly, in a particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the amount of the at least one monomer B in the final product is from 3 to 10 wt%.

When the amount of polymer B in the final polymer is from 10 to 25 wt%, a substantial improvement of impact properties is obtained whereas the mechanical properties of the product are maintained, and so there is no need to incorporate impact modifiers to the polymer. Additionally, these polymers are also characterized by having a high apparent density. Accordingly, in a more particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the amount of the at least one monomer B in the final product is from 10 to 25 wt%. When more than one monomer A is used in the process of the invention, the monomers can be equal or different in all the steps of the process where monomer A is added. Similarly, when more than one monomer B is used in the process of the invention, the monomers can be equal or different in all the steps of the process where monomer B is added. Particularly, when more than one monomer A is used, at least one of the monomers A is present in all the steps of the process where monomer A is added. Also particularly, when more than one monomer B is used, at least one of the monomers B is present in all the steps of the process where monomer B is added.

The process of the invention is carried out by loading in the reactor water, a solution of at least a suitable amphiphilic substance and adding totally or partially a mixture of at least one monomer A and at least one monomer B to the reactor. The amount of the at least one monomer B added at step a) is from 10 to 100 wt% of the total amount of monomer B, and the amount of the at least one monomer A added at step a) is from 10 to 100 wt%, particularly from 50 to 100 wt%, of the total amount of monomer A.

In a particular embodiment, monomer A in step b) is added in one or more injections.

In another particular embodiment, monomer B in step b) is added in one or more injections.

In another particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, in step a) the polymerization reaction is carried out by mixing from 50 to 100 wt%, or from 60 to 100 wt%, of the total amount of the at least one monomer B, and from 30 to 100 wt%, or from 50 to 100 wt%, or from 60 to 100 wt%, of the total amount of the at least one monomer A. In a more particular embodiment, optionally in combination with one or more features of the particular embodiments defined above or below, the polymerization reaction is carried out by mixing in step a) the 100 wt% of the at least one monomer B, and the 100 wt% of the at least one monomer A, and the mixture is allowed to react until the conversion of the monomers reaches a value higher than higher than 70 wt%, and particularly higher than 80 wt%. In this step at least one appropriate amphiphilic substance is added. The addition of the at least one amphiphilic substance can be made continuously or in one or more injections. At least one initiator is injected either as a shot or semicontinuously in order to start polymerization. By "appropriate temperature" it is meant the required temperature to carry out the polymerization of the monomer or monomers. Generally, an appropriate polymerization temperature is considered a working temperature such as from 20 to 80°C, more particularly from 25 to 80°C, or even more particularly from 30 to 75°C.The temperature is adjusted according to the reactivity and the amount of the initiator. The reactor can be maintained at the same temperature or use a temperature profile.

The amount of the initiator or blend of different initiators added in step a) is from 0.001 to 2 mol%, particularly from 0.001 to 1 .5 mol%, and more particularly from 0.001 to 1 .0 mol% with respect to the total amount of monomer added in this step. The addition can be made continuously or in one or more injections, particularly in one or more injections.

The reaction is maintained at the adjusted temperature until reaching a conversion from 10 to 99 wt%, particularly from 20 to 80 wt%.

Methods to determine monomer conversion are known for those skilled in the art and include among others off-line gravimetry (JM Goldwasser and A Rudin, J. Polym. Sci. Polym. Chem. ED., 1982, Vol. 20, p. 1993) and on-line reaction calorimetry (A Urretabizkaia, et al. J. Polym. Sci. Part A: Polym. Chem., 1994; Vol. 32, p. 1761 ). As used herein, the term "conversion" stands for the quotient of polymer weight/(polymer weight + monomer weight).

In the case that not the whole amount of either monomer A or monomer B has been added in step a, the remaining amount of either monomer A or monomer B can be added during step b). The addition can be made continuously or in one or more injections, preferably in one or more injections. In a particular embodiment, the addition of the remaining amount of either monomer A or monomer B during step b) is made in one injection.

Also in this step, optionally, an additional amount of the at least one appropriate amphiphilic substance can be added. The addition of the at least one amphiphilic substance can be made continuously or in one or more injections.

Also optionally, and independently of the possible addition of amphiphilic substances, an additional amount a suitable initiator or a blend of different initiators can be added. This amount is from 0.001 to 2 mol%, particularly from 0.001 to 1 .5 mol%, and more particularly from 0.001 to 1 .0 mol% with respect to the total amount of monomer added in this step. The addition can be made continuously or in one or more injections, particularly in one or more injections.

Additionally, independently of the possible addition of amphiphilic substances and/or initiators, an amount of buffer can be optionally added, particularly from 0.001 to 1 g/l of water, more particularly from 0.01 to 1 g/l of water, and even more particularly from 0.05 to 1 g/l of water.

Then, the reaction is conducted until the conversion of the monomers reaches a value higher than 20 wt%, preferably higher than 50 wt%, more preferably higher than 70 wt% and even more preferable higher than 80 wt%.

There is no limitation concerning the moment when the injections during step b) are carried out, or on the number of injections.

In steps a) and b) additional amounts of water can also be loaded into the reactor. The addition can be made continuously or in one or more injections.

Particularly, the process of the invention is carried out in oxygen free atmosphere. The oxygen of the reactor can be removed before starting the polymerization reaction of step a) by using a purge with an inert gas such as of nitrogen or argon, by vacuum or by a combination of inert gas and vacuum.

The reaction can be carried out in conventional reactors. As an instance, for the reaction of vinyl halides and other monomers in aqueous medium a stirred tank reactor with or without reflux condenser can be used.

The initiator added in steps a) and b) is selected from the group consisting of thermal and redox initiators. The radical initiator can be used without any limitation regarding their water solubility. Suitable thermal initiators are well known in the art and include, but are not limited to, inorganic peroxides, such as ammonium peroxodisulfate, sodium peroxodisulfate, potassium peroxodisulfate, and hydrogen peroxide; organic peroxides, including percarbonates such as di(2-ethylhexyl) peroxydicarbonate, 1 ,1 ,3,3- tetramethyl butyl 1 .peroxyneodecanoate diacyl peroxides such as dibenzoyl peroxide, alkyl peroxides such as tert-butyl hydroperoxide, benzoil peroxide, lauroyl peroxide, cumyl hydroperoxide, dialkyl peroxides such as di-tert-butyl hydroperoxide, diisobutyryl peroxide and acyl alkyl peroxides such as tert- butyl peroxybenzoate; and azo initiators, such as 2,2'-azobis(2- methylbutyronitrile), 2,2'-azobis(2-methylpropio-nitrile), 2,2'-azobisiso- butyronitrile and the like. Examples of redox initiators include, but are not limited to, inorganic peroxides paired with a suitable reducing agent such as sulfites, metabisulfites, sodium dithionite, sodium thiosulfate, sodium formaldehydesulphoxylate, a mixture of disodium salt of 2-hydroxy-2- sulphinoacid, of sodium sulphite and of disodium salt of 2-hydroxy-2- sulphoacid, or a mixture of disodium salt of hydroxysulphinoacetic acid and of disodium salt of hydroxysulphoacetic acid; and tert-butyl hydroperoxide and hydrogen peroxide paired with ascorbic acid, a mixture of disodium salt of 2- hydroxy-2-sulphinoacid, of sodium sulphite and of disodium salt of 2-hydroxy- 2-sulphoacid, or a mixture of disodium salt of hydroxysulphinoacetic acid and of disodium salt of hydroxysulphoacetic acid. Water soluble initiators are preferred. The polymerization process in aqueous medium of this invention can be carried out in suspension, emulsion or microsuspension. Accordingly, the aqueous phase contains at least an amphiphilic substance which helps to stabilize the dispersion. The selection of the amphiphilic substance will depend on the kind of polymerization process. Both suspension agents and surfactants (emulsifiers) can be used.

Suitable suspending agents include, but are not limited to, partially hydrolysed vinyl alcohol polymers, cellulose ethers or hydroxides, gelatine, starch, vinyl acetate-maleic anhydride copolymers, ethylene-vinyl acetate copolymers, alginates, esters of fatty acids with glycerol, ethylene glycol or pentaerythritol, and sorbitan monolaurate, or mixtures thereof. Preferred suspending agents are polyvinyl alcohol) with a degree of hydrolysis of 70- 90 mol% and a viscosity of 5-60 mPa-s in a 4% (w/w) aqueous solution, hydroxypropyl methylcellulose with a 23-30 wt% of groups methoxy, a 6-10 wt% hydroxypropyl groups and a viscosity of 12-120 mPa-s in a 2% (w/w) aqueous solution, or mixtures thereof. The optimum amount of suspending agent depends on its nature, the desired particle size, the design of the reactor and the stirrer, the water/monomer proportion and the stirring speed, and can be chosen by one skilled in the art.

The amount of suspending agent that can be added in each step with respect to the total amount of monomers in each step is from 100 to 20000 ppm, particularly from 200 to 15000 ppm, more particularly from 300 to 10000 ppm.

Suitable emulsifiers include, but are not limited to, those selected from the group consisting of anionic emulsifiers, cationic emulsifiers, non-ionic emulsifiers, and mixtures thereof. Anionic and non-ionic emulsifiers are preferred. Emulsifiers used in the present invention may contain one or more olefinically unsaturated group (reactive emulsifiers). Polymeric or oligomeric emulsifiers can also be used. Examples of anionic emulsifiers include, but are not limited to, alkyl sulfates such as sodium lauryl sulfate, alkyl-aryl sulfonates such as sodium dodecylbenzene sulfonate, polyoxyethylene alkyl ether sulfates, polyoxyethylene alkylphenyl ether sulfates, and diphenyl sulfonate derivatives.

Suitable non-ionic emulsifiers include, but are not limited to, polyoxyethylene alkyl ethers and polyoxyethylene alkylphenyl ethers.

Suitable reactive emulsifiers include, but are not limited to, polyoxyethylene alkylphenyl ethers; polyoxyethylene alkylphenyl ether ammonium sulfates; sodium allyloxy hydroxypropyl sulphonate and allylsulphosuccinate derivatives.

Suitable polymeric emulsifiers include, but are not limited to, copolymers of acrylic and methacrylic monomers.

These emulsifiers may be used alone or in combination of two or more thereof. The amount of the emulsifier that can be added in each step is, for example, from 0.2 to 10 parts by weight, particularly from 0.5 to 5 parts by weight, per 100 parts by weight with respect to the total amount of monomers in each step. A buffer may be used in the polymerization process in order to maintain the pH of the reaction. Typical buffers can include alkaline salts of inorganic and organic acids, able to keep the pH of water solutions in the range 8-10. These buffers include, but are not limited to, sodium bicarbonate (NaHCO ₃ ), sodium dihydrogen phosphate (NaH ₂ PO ₄ ) disodium phosphate (Na ₂ HPO ₄ ), sodium acetate (CH ₃ COONa), or the potassium or ammonium salts thereof. The reaction mixture will optionally contain from 0.001 to 1 g/l of water, particularly from 0.01 to 1 g/l of water, and more particularly from 0.05 to 1 g/l of water of a buffer. Suitable monomers B intervening in the polymerization reaction include, but are not limited to, acrylates and other monomers such as vinyl benzoate, isobutylene, dialkyl maleate, di-alkyl fumarate, vinyl decanoate and its isomers, vinyl esters of versatic acid including VeoVa (™Momentive) monomers and vinyl acetate. Particularly, the monomer B is an acrylate, namely, an ester of acrylic acid. Examples of acrylates include, but are not limited to, methyl, ethyl, 2-methoxyethyl, 2-ethoxyethyl, isopropyl, n-butyl, iso- butyl, sec-butyl, tert-butyl, hexyl, 2-ethylhexyl, octyl, iso-octyl, lauryl, isodecyl, octadecyl, dodecyl, 4-butyl cyclohexyl, hexadecyl, benzyl, tetrahydrofurfuryl, diethylene glycol diethyl ether, and methoxy (polyethylene glycol) acrylate, and acrylates with a hydrophilic character such as 2-hydroxyethyl, hydroxypropyl, and 4-hydroxybutyl acrylate, and hydroxyacrylate.

Particularly, monomer B is an acrylate selected from the group consisting of butyl acrylate, isooctylacrylate, methylacrylate, ethyl acrylate and 2-ethylhexyl acrylate.

The content of monomer B in the product can be from 0.3 to 45 wt% based on the weight of the vinyl halides. Particularly, the content of monomer B is from 3 to 45 wt%, more particularly from 3 to 33.3 wt%, based on the weight of the vinyl halides in the product.

Depending on the selected monomer B, the properties of the obtained polymer can be tuned to meet the requirements for different applications by adjusting the ratio between monomers B and A in the overall formulation.

Suitable vinyl halide monomers include, but are not limited to, vinyl chloride and its structurally related derivatives, including vinylidene chloride and 2- chloropropene. In any of the embodiments of the invention, one vinyl halide monomer can be vinyl chloride. Particularly, the vinyl halide monomer (monomer A) used in the process as defined above is from 75% to 100% vinyl chloride.

Once the reaction is finished, the unreacted vinyl halide can be recovered by depressurizing the reactor and vacuum distillation, the slurry with the powder of the resin dispersed in water can be stripped, and the product can be isolated by filtration or centrifugation of the resulting product, followed by washing with water and drying.

Depending on the specific monomers and their content in the final product, a variety of rigid or semi-rigid polyvinyl halide) materials with modified properties are obtained.

The appropriate monomers and their content for the aimed specific application of the final product can be easily determined by a skilled person in the art with the help of the teachings of the examples given in this description. As mentioned above, the polymerization process in aqueous medium of this invention can be carried out in suspension, emulsion or microsuspension. The selection of the type of polymerization can be made according to the intended applications of the products obtained. As an instance, the polymerization process of the invention can be carried out in aqueous suspension.

When the polymerization process is in suspension, it can be carried out in deionised water, being the weight to weight ratio of water with respect to total amount total monomers from 0.8 to 4 wt / wt, particularly from 1 to 3 wt /wt.

As commented above, an inherent result of the process of the invention is that it provides a new range of products from at least one vinyl halide monomer and at least one another monomer B with improved mechanical properties, particularly an with an increased apparent density and impact strength. These properties make the product of the invention particularly suitable to use as a raw material in the production of different articles of manufacture for multiple applications.

Such improved properties indicate that the product obtainable by the process of the invention is different to the vinyl halide products of the prior art.

The products of the invention can be formulated in a similar way to commercial polyvinyl halide) resins, adding suitable additives for specific applications and using the same processing equipment, thus obtaining a variety of polyvinyl halide) compounds with different properties suitable for different applications.

The applications of the products obtained by the process of the invention are not at all limited, and include all types of rigid and semirigid articles manufactured by injection, extrusion, calendaring, extrusion blow moulding, thermoforming, vacuum moulding, and so on, with a large number of applications.

Throughout the description and claims the word "comprise" and variations of the word, are not intended to exclude other technical features, additives, components, or steps. Furthermore, the word "comprise" encompasses the case of "consisting of. The following examples are provided by way of illustration, and they are not intended to be limiting of the present invention. Furthermore, the present invention covers all possible combinations of particular and preferred embodiments described herein.

EXAMPLES

In examples below, the characterization of products was carried out using the following methods and equipments:

The molecular weight distribution expressed as Mn (number average molecular weight) and Mw (weight averaged molecular weight) were measured by Gel Permeation Chromatography (GPC). The chromatograph used from Waters, Model 717 Autosampler, has two detectors, one of refractive index, Waters 2410, and other UV absorption, Waters 2487. The analysis was conducted at 35° C using tetrahydrofuran (THF) as eluent and the results are based on polystyrene (PS) standards.

The apparent density of the resin was determined according to the method described in UNE-EN ISO 60.

The percentage of monomers in the polymer was calculated using the carbonyl peak appearing at 1 ,723 cm ^"1 from the FTIR spectra obtained in a Nicolet iS5 with an ATR equipment iD5 from Thermo. The density was evaluated according to the UNE-EN ISO 1 183-1 . The density of the product is the true density of the solid polymer and does not include any pore. The apparent density of the resin in powder form is lower than the density of the product because these particles contain plenty of pores. Additionally to evaluate certain properties of products it was necessary to obtain pressed sheets that were prepared by formulating products with 3 phr of an organic one pack stabilizer and 2 phr of lubricant, wherein "phr" is an abbreviation for "parts per hundred parts of resin". Formulations were fused and homogenized in a two-roll mill at a temperature of 160-180°C and pressed at 160-175°C to mould the specific samples of each test.

The Shore A and D hardness was determined using the indentation method by means of a durometer as is described in the UNE-EN ISO 868 standard.

Tensile properties were determined in an INSTRON 4301 according to the UNE-EN ISO 527 standard. The Izod Impact strength properties were evaluated according UNE-EN ISO 180 using notched samples. The thermal behaviour of products were evaluated using a Dynamic Mechanical Thermal Analysis (DMTA) in a Triton DMA equipment under conditions of "single cantilever bending" at a frequency of 1 Hz and a heating rate 4 ° C/min in a temperature range from -50 °C to 120 °C. From this test, temperature transitions (glass temperature, T _g ) were obtained.

Static thermal stability tests were applied to the products. Pressed samples were prepared by adding to the products 2 phr of an organic stabilizer and 3 phr of epoxidized soy bean oil. The samples were heated in a Werner-Mathis oven at 180°C and withdrawn therefrom at regular intervals of 10 minutes during 70 minutes.

The fusion behaviour of the products was evaluated in Brabender Plasticorder equipment at 180°C and 50 rpm using 3 phr of an organic stabiliser and 0.5 phr of external wax to avoid the stickiness to metal parts.

The products obtained using this procedure were also compared with conventional PVC resin (comparative example 1 ), with the products described in comparatives examples 2 and 3 obtained using the procedure described in US20090143547, with comparative examples 4 and 5 in which methyl methacrylate was used, and with the product of comparative example 6 obtained using the procedure described in WO 2013014158.

COMPARATIVE EXAMPLE 1

In a reactor of 7.5 litre equipped with a stirrer, cooling/heating jacket, injection pipette, load pump, dosing pump, and a computerized control system, 3,400 ml of deionized water and 80.6 g of a 5.7 wt% solution in deionized water of a mixture of suspending agents were loaded. The solution of suspending agents consisted of two types of polyvinyl alcohols with 80 and 88% hydrolysis degree, respectively, and a hydroxypropyl methylcellulose with a viscosity of 50 mPa s. The percentage in weight of each suspending agent in the solution was 54% wt, 25% wt and 21 % wt respectively. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,318 g of VCM were loaded and the reaction mixture was heated to 55.7 °C.

When this temperature was achieved, 3.25 g of a 60 wt% emulsion of di-(2- ethyl-hexyl) peroxydicarbonate and 0.65 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate were injected into the reactor

The reaction was finished when the reactor pressure dropped 3.0 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,935 g of product.

The apparent density of the resin was 0.527 g/cm ³ . It had only one T _g at 85 °C determined by DMTA and molecular weights were Mn 79,000 and Mw 145,000.

The product had a density of 1 .38 g/cm ³ , a Shore hardness A/D of 97/82, a tensile strength of 56.7 MPa, an elongation at break of 213% and 3 KJ/m ² of Izod impact strength.

COMPARATIVE EXAMPLE 2

In the same reactor described in Comparative example 1 , 2,943 ml of deionized water, 41 g of a 5.8 wt% solution in deionized water of a polyvinyl alcohol with a hydrolysis degree of 78% wt in deionized water, 1 .2 g of butyl acrylate and 6 g of methyl methacrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2975 g of VCM were loaded and the reaction mixture was heated to 64 °C.

When this temperature was reached, 0,05 g of a 50 wt % emulsion of tert- butyl peroxyneodecanoate was injected into the reactor.

The reaction was maintained in these conditions during 5 hours and then the un-reacted vinyl chloride was removed by depressurizing the reactor. The obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 121 g of product.

The apparent density of the resin was 0.1 10 g/cm ³ and the polybutylacrylate content determined by FTIR was 3% wt.

The Mn and Mw were 45,600 and 88,100, respectively, and the product had one Tg at 84 °C.

The apparent density of the obtained polymer was very low, because the reaction was carried out with a low amount of initiator and in consequence with a low conversion of the monomers of about 4,7% wt.

The product had a density of 1 .33 g/cm ³ , a Shore hardness AID of 94 / 76. It was not possible to determine mechanical properties because the product did not fuse in two roll mill even using higher temperature and longer time. COMPARATIVE EXAMPLE 3

In the same reactor described in Comparative Example 1 , 2,943 ml of deionized water, 41 g of a 5.8 wt% solution in deionized water of a polyvinyl alcohol with a hydrolysis degree of 78% in deionized water, 1 .2 g of butyl acrylate and 6 g of methyl methacrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,975 g of VCM were loaded and the reaction mixture was heated to 64 °C.

When this temperature was reached, 2.49 g of a 50 wt % emulsion of tert- butyl peroxyneodecanoate was injected into the reactor. The reaction was maintained in these conditions during 5 hours until reaching a conversion of about 80%, and then the un-reacted vinyl chloride was removed by depressurizing the reactor. The obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 2,398 g of product.

The apparent density of the resin was 0.565 g/cm ³ and the polyacrylates content determined by FTIR was 2% wt. It had only one T _g at 85 °C determined by DMTA and the molecular weights were Mn 55,000 and Mw 1 17,100.

The product had a density of 1 .37 g/cm ³ , a Shore hardness A D of 97/80, a tensile strength of 47.5 MPa, an elongation at break of 154% and an Izod impact strength of 4 KJ/m ² .

COMPARATIVE EXAMPLE 4 In the same reactor described in Comparative Example 1 , 3,396 ml of deionized water, 82 g of a 5.7 wt% solution in deionized water of a polyvinyl alcohol with a hydrolysis degree of 78% in deionized water, 57.5 g of butyl acrylate and 57.5 g of methyl methacrylate were loaded. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 51 °C. When this temperature was reached, 3.24 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate was injected into the reactor

The reaction was maintained in these conditions during 8 hours and then the un-reacted vinyl chloride was removed by depressurizing the reactor. The obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 250 g of product.

The apparent density of the resin was 0.385 g/cm ³ , and the polyacrylate content determined by FTIR was 9% wt. The Mn and Mw were 52,300 and 102,300 respectively and the product had one Tg at 68 °C. The product had a density of 1 .13 g/cm ³ , a Shore hardness AID of 86 / 38, a tensile strength of 48.4 MPa, an elongation at break of 154%, and an Izod impact strength of 3 KJ/m ² . COMPARATIVE EXAMPLE 5

In the same reactor described in Comparative Example 1 , 3,390 ml of deionized water, 87 g of a 5.3 wt% solution in deionized water of a polyvinyl alcohol with a hydrolysis degree of 78% in deionized water 1 15 g of methyl methacrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 51 °C.

When this temperature was reached, 3.24 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate was injected into the reactor The reaction was maintained in these conditions during 8.3 hours and then the un-reacted vinyl chloride was removed by depressurizing the reactor. The obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 180 g of product.

The apparent density of the resin was 0.180 g/cm ³ and a polymethylmetacrylate content determined by FTIR was 24% wt.

The Mn and Mw were 25,400 and 51 ,900, respectively, and the product had one Tg at 93 °C.

The product obtained has a very poor mechanical properties tensile strength 9.3 MPa and elongation at break 1 %. It had a density of 1 .06 g/cm ³ , a Shore hardness AID of 93/65.

COMPARATIVE EXAMPLE 6 This comparative example illustrates the process disclosed in WO2013014158 and the obtained copolymer, particularly having a 24% wt of polybutyl acrylate. In the same reactor described in Comparative Example 1 , 3200 g of deionized water, 104 g of a 5.7 wt% aqueous solution of a polyvinyl alcohol with a hydrolysis degree of 72.5%, 2.4 g of sodium bicarbonate, 0.17 g of cetyltrimethylammonium bromide, 6.09 g of iodoform, and 60.9 g of butyl acrylate were loaded. Once stirring was connected, and the air on the reactor evacuated, and while heating in order to reach a temperature of 42 °C, 1530 g of vinyl chloride were loaded, followed by the injection of a freshly prepared solution of 18.82 g of sodium dithionite (85% purity) in 50 ml of deionized water. Feeding of the rest of acrylate was initiated immediately. The feeding was carried out during 3.5 hours at a decreasing flow rate, so that after 37 min a total of 0.77 mol of butyl acrylate were added, after 97 min 1 .43 mol, after 150 min 1 .65 mol, and after 210 min 1 .74 mol. At this moment, the acrylate feed was stopped. After 150 min of the acrylate dosing was initiated, a new freshly prepared solution of 6,22 g of sodium dithionite (85% purity) in 50 ml of deionized water was injected to the reactor. The temperature was kept at 42 °C throughout. After 150 min of reaction under the same conditions, the reactor was depressurized. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1460 g of product

The apparent density of the resin was 0.330 g/cm ³ and and the Mn and Mw were 83,100 and 139,900, respectively. The product had one Tg at 55 The polybutylacrylate content determined by FTIR was 24 wt%.

The product had a density of 1 .3 g/cm ³ , a Shore hardness A/D of 94 / 76, a tensile strength of 50.9 MPa, an elongation at break of 209% and an Izod impact strength of 4 KJ/m.

EXAMPLE 1

In the same reactor described in Comparative Examplel , 2,700 ml of deionized water, 81 .3 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 230 g of 2-ethyl hexyl acrylate were loaded. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 1 ,868 g of VCM were loaded and the reaction mixture was heated to 46 °C. When this temperature was achieved, a continuous feeding of 0.395 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 253 minutes. After 2 and 3 hours from the start of the feeding of initiator, two injections of 105 g of VCM were introduced into the reactor.

The reaction was finished when the reactor pressure dropped 3.0 bars. The un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,831 g of product. The apparent density of the resin was 0.721 g/cm ³ and the Mn and Mw were 105,400 and 235,400, respectively. The product had two Tgs one at 83 °C and the second one at 29°C.

The poly-ethylhexylacrylate content determined by FTIR was 12 wt%.

The product had a density of 1 .32 g/cm ³ , a Shore hardness A D of 96 / 78, a tensile strength of 43.5 MPa, an elongation at break of 209% and an Izod impact strength of 5 KJ/m ² . EXAMPLE 2

In the same reactor described in Comparative Example 1 , 2,675 ml of deionized water, 54.7 g of a 5.0 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 , and 68 g of 2-ethyl-hexyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 48 °C. When this temperature was achieved, a continuous feeding of 0.357 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 206 minutes.

The reaction was finished when the reactor pressure drop 3.7 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,947 g of product.

The density of the resin was 0.643 g/cm ³ . The Mn and Mw were 72,800 and 171 ,000, respectively. The product had one Tg at 84°C.

The poly-ethylhexylacrylate content determined by FTIR was 4 wt%.

The product had a density of 1 .36 g/cm ³ , a Shore hardness A/D of 97/ 84, a tensile strength of 57.0 MPa, an elongation at break of 183%, and an Izod impact strength of 5 KJ/m ² .

EXAMPLE 3

In the same reactor described in Comparative Example 1 , 3,385 ml of deionized water, 93.0 g of a 5.0 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example l and 1 15 g of ethyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 51 °C.

When this temperature was reached, 3.24 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate was injected into the reactor. The reaction was finished when the reactor pressure dropped 3.0 bars and the un- reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,955 g of product. The apparent density of the resin was 0.619 g/cm ³ and the Mn and Mw were 84,400 and 172,300, respectively. The product had one Tg at 85 °C.

The poly-ethylacrylate content determined by FTIR was 3 wt%. The product had a density of 1 .36 g/cm ³ , a Shore hardness A D of 95 / 80, a tensile strength of 46.2 MPa, an elongation at break of 202%, an Izod impact strength of 4 KJ/m ² .

EXAMPLE 4

In the same reactor used in Comparative Example 1 , 2,700 ml of deionized water, 81 .8 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 348 g of butyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 1 ,975g of VCM were loaded and the reaction mixture was heated to 46 °C. When this temperature was achieved, a continuous feeding of 0.476 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 300 minutes.

The reaction was finished when the reactor pressure dropped 3.2 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 2,022 g of product.

The apparent density of the resin was 0.790 g/cm ³ and the Mn and Mw were 95,800 and 243,900, respectively. The product had two Tgs one at 84 °C and the second one at 36°C. The content of poly-butylacrylate determined by FTIR was 21 wt%.

The product had a density of 1 .32 g/cm ³ , a Shore hardness A/D of 98 / 75, a tensile strength of 44.0 MPa, an elongation at break of 217%, and an Izod impact strength of 10 KJ/m ² .

EXAMPLE 5

In the same reactor described in Comparative Example 1 , 2,700 ml of deionized water, 55.5 g of a 5.0 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 92 g of 2-ethyl hexyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,025 g of VCM were loaded and the reaction mixture was heated to 51 °C.

When this temperature was achieved a continuous feeding of 0.424 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 218 minutes. After one hour of reaction under these conditions, a constant feeding of 122.5 g /h of 2-ethyl hexyl acrylate was maintained for 90 minutes.

The reaction was finished when the reactor pressure dropped 3.6 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,998 g of product. The apparent density of the resin was 0.662 g/cm ³ and the Mn and Mw were 72,150 and 179,200, respectively. The product had one Tg at 77 °C.

The content of poly-ethylhexylacrylate determined by FTIR was 1 1 wt%. The product had a density of 1 .31 g/cm ³ , a Shore hardness A/D of 96/ 78, a tensile strength of 45.8 MPa, an elongation at break of 220%, and an Izod impact strength of 8 KJ/m ² . EXAMPLE 6

In the same reactor described in Comparative Example 1 , 2,700 ml of deionized water, 81 .3 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 230 g of 2-ethyl hexyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,078 g of VCM were loaded and the reaction mixture was heated to 46 °C. When this temperature was achieved, a continuous feeding of 0.404 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 267 minutes.

The reaction was finished when the reactor pressure dropped 3.0 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,926 g of product.

The apparent density of the resin was 0.709 g/cm ³ and the Mn and Mw were 87,000 and 223,800, respectively. The product had two Tgs one at 83 °C and the second at 31 °C.

The content of poly-ethylhexylacrylate determined by FTIR was 10 wt%.

The product had a density of 1 .32 g/cm ³ , a Shore hardness A D of 96/ 77, a tensile strength of 44.4 MPa, an elongation at break of 189%, and an Izod impact strength of 13 KJ/m ² .

EXAMPLE 7

In the same reactor described in Comparative Example 1 , 2,675 ml of deionized water, 86.3 g of a 5.3% wt solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 92 g of butyl acrylate were loaded. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 64 °C. When this temperature was achieved a continuous feeding of 0.345 L of a 0.86 wt% emulsion of diisobutyryl peroxide were dosed during 302 minutes.

The reaction was finished when the reactor pressure dropped 3.3 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,786 g of product. The apparent density was 0.651 g/cm ³ . The Mn and Mw were 47,700 and 103,000, respectively. The product had one Tg at 83 °C.

The content of poly-butylacrylate determined by FTIR was 5 wt%. The product had a density of 1 .36 g/cm ³ , a Shore hardness AID of 97/79 a tensile strength of 54.0 MPa, an elongation at break of 163%, and an Izod impact strength of 5 KJ/m ² .

EXAMPLE 8

In the same reactor described in Comparative Example 1 , 2,700 ml of deionized water, 87.1 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 463 g of butyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 1850 g of VCM were loaded and the reaction mixture was heated to 46 °C.

When this temperature was achieved, a continuous feeding of 0.473 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 285 minutes The reaction was finished when the reactor pressure dropped 3.2 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,957 g of product.

The apparent density of the resin was 0.736 g/cm ³ and and the Mn and Mw were 105,600 and 302,000, respectively. The product had two Tgs one at 83 ant the second at 50°C.

The content of poly(butyl acrylate) determined by FTIR was 25 wt%.

The product had a density of 1 .3 g/cm ³ , a Shore hardness A/D of 96 / 70, a tensile strength of 33.0 MPa, an elongation at break of 229%, and an Izod impact strength of 100 KJ/m ² .

EXAMPLE 9 In the same reactor described in Comparative Examplel , 2,700 ml of deionized water, 81 .3 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 , and 230 g of 2-ethyl hexyl acrylate were loaded. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,078 g of VCM were loaded and the reaction mixture was heated to 51 °C. When this temperature was achieved 3.2 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate were injected into the reactor. The reaction was maintained under these conditions and 1 .4 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate were injected after two hours.

The reaction was finished when the reactor pressure dropped 3.0 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,969 g of product. The apparent density of the resin was 0.679 g/cm ³ . The Mn and Mw were 78,000 and 183,900, respectively. The product had two Tgs one at 83 and the second at 31 °C.

The content of poly-ethylhexylacrylate determined by FTIR was 1 1 wt%.

The product had a density of 1 .32 g/cm ³ , a Shore hardness A/D of 96 / 78, a tensile strength of 37.8 MPa, an elongation at break of 169%, and an Izod impact strength of 7 KJ/m ² . EXAMPLE 10

In the same reactor described in Comparative Example 1 , 2700 ml of deionized water, 81 .8 g of a 5.7 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 348 g of 2-ethyl hexyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 1 ,975 g of VCM were loaded and the reaction mixture was heated to 46 °C. When this temperature was achieved, a continuous feeding of 0.379 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 243 minutes.

The reaction was finished when the reactor pressure dropped 3.2 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,987 g of product. The apparent density of the resin was 0.747 g/cm. The Mn and Mw were 89,800 and 247,900 respectively. The product had two Tgs one at 84 and the second at 30°C. The content of poly-ethylhexylacrylate determined by FTIR was 14 wt%.

The product had a density of 1 .29 g/cm ³ , a Shore hardness A/D of 95/70, a tensile strength of 33.1 MPa, an elongation at break of 165%, and an Izod impact strength of 109 KJ/m ² .

EXAMPLE 1 1 In the same reactor described in Comparative Example 1 , 2,675 ml of deionized water, 86.2 g of a 5.3 wt% solution in deionized water of the mixture of suspending agents defined in Comparative Example 1 and 69 g of 2-ethyl hexyl acrylate and 69 g of butyl acrylate were loaded. Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,150 g of VCM were loaded and the reaction mixture was heated to 55.7 °C. When this temperature was achieved, 3.20 g of a 60 wt% emulsion of di-(2- ethyl-hexyl) peroxydicarbonate and 0.64 g of a 50 wt% emulsion of 1 ,1 ,3,3 tetra-methyl butyl peroxyneodecanoate were injected into the reactor

The reaction was finished when the reactor pressure dropped 3.0 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,817 g of product. The apparent density of the resin was 0.796 g/cm ³ . The Mn and Mw were 63,700 and 139,900 respectively. The product had a Tg at 83°C.

The content of polyacrylates determined by FTIR was 10 wt%. The product had a density of 1 .35 g/cm ³ , a Shore hardness A/D of 97 / 80 a tensile strength of 49.4 MPa, an elongation at break of 190 %, an Izod impact strength of 6 KJ/m ² . EXAMPLE 12

In the same reactor described in Comparative Example 1 , 2,700 ml of deionized water, 92.7 g of a 5.0 wt% solution in deionized water the mixture of suspending agents defined in Comparative Example 1 and 1 15 g of 2-ethyl hexyl acrylate were loaded.

Once the reactor was closed and the stirrer was connected at 150 rpm, vacuum was applied till removing most of the oxygen present in the reaction medium. Then, the stirring was increased to 300 rpm, 2,200 g of VCM were loaded and the reaction mixture was heated to 69 °C. When this temperature was achieved, a continuous feeding of 0.307 L of a 0.86 wt% emulsion of diisobutyryl peroxide was dosed during 191 minutes.

The reaction was finished when the reactor pressure dropped 3.0 bars and the un-reacted vinyl chloride was removed by depressurizing the reactor. Then, the obtained suspension was separated by filtration, washed three times with deionized water, and dried with air in a fluidized bed dryer obtaining 1 ,754 g of product.

The apparent density of the resin was 0.643 g/cm ³ . The Mn and Mw were 75,700 and 247,900 respectively. The product had a Tg at 82°C. The content of poly-ethylhexylacrylate determined by FTIR was 5 wt%.

The product had a density of 1 .35 g/cm ³ , a Shore hardness AID of 97 / 80, a tensile strength of 50.7 MPa, an elongation at break of 175%and an Izod impact strength of 3 KJ/m ²

COMPARATIVE EXAMPLE 7 -Apparent density and Impact properties

Table 1 presents a comparison of the properties of the polymers of the present invention with those of the polymers obtained in Comparative Examples 1 to 6.

It can be clearly seen that the invention allows obtaining polymers with substantially higher apparent density of the resin that leads to an significant increase of the productivity in subsequent processing steps and the products have also a higher Izod impact strength than those obtained in the prior art (Comparative examples 1 to 6).

Table 1

Apparent density Izod Impact

EXAMPLE

(g/cm ³ ) Strength (KJ/m ² )

UNE-EN ISO 60 UNE-EN ISO 180

Comparative Example 1 0.527 3

Comparative Example 2 0.110 2

Comparative Example 3 0.565 4

Comparative Example 4 0.385 3

Comparative Example 5 0.180 -

Comparative Example 6 0.330 4

Example 1 0.721 5

Example 2 0.643 3

Example 3 0.619 4

Example 4 0.790 10

Example 5 0.662 8

Example 6 0.709 13

Example 7 0.651 5

Example 8 0.736 100

Example 9 0.679 7

Example 10 0.747 109

Example 1 1 0.796 6

Example 12 0.643 3 COMPARATIVE EXAMPLE 8 -Fusion behaviour

The fusion behaviour of the products obtained in Comparative Example 1 (common PVC resin) and in Example 1 1 was analysed in a Brabender Plasticorder equipment at 180°C and 50 rpm. Fig. 1 shows the curves obtained in this test and in Table 2 are summarised the main parameters obtained.

TABLE 2.

The fusion time is the time between the time from the peak of loading the chamber and the time where the maximum torque is reached. In Fig. 1 and Table 2 are pointed out that the fusion time is significantly shorter in the product obtained using the procedure of the invention than in common PVC resin (30 with respect to 40 seconds).

In addition, the final viscosity of product is not modified as proved by the same torque recorded in both analyses. COMPARATIVE EXAMPLE 9 - Homogeneity

DMTA tests carried out on polymers obtained in Comparative Example 6 and in Example 8 showed that the products of Comparative Example 6 had an unique T _g at about 56 °C (see Fig. 2). This implies a homogeneous product in which the units of vinyl halide monomer and acrylic monomer are homogenously distributed along the polymer chains.

In contrast it can be seen that the polymer of Example 8 had two Tgs; the one appearing at higher temperatures (85°C) is related to the presence of PVC rich chains and the presence of these PVC rich chains reduces significantly the stickiness of the final product making it much easier to handle and to dry. At the same time this broadens the temperatures at which the products can be used.

COMPARATIVE EXAMPLE 10- Thermal stability

A key characteristic that is influenced by the monomer distribution is the thermal stability of the products that were analyzed using a thermogravimetric analysis (TGA). This test gives information about the steps of the degradation process, the temperatures at which each degradation process starts and finishes, and the type of products formed in each step.

A Thermobalance High Resolution TA Instruments Q500 model TG incorporating a spectrophotometer Fourier Transform Infrared (FTIR) Nicolet model 6700 was used. The tests were performed on samples in powder form under a nitrogen flow of 90 cm ³ /min and a constant heating rate of 10 °C/min, from 40 °C to 700 °C. Fig. 3 shows the TGA results of the two copolymers. It can be seen that the product obtained in Example 8 was more stable than the one obtained in Comparative Example 6.

From TGA test the temperature at which the degradation starts can be determined using different criteria. T, is the temperature of the start of the weight loss; T, ₍₅₎ is the temperature at which the material has lost 5% of its initial weight and T, ( _0nse t) is temperature given by the intersection of the tangents to the TGA curve at the start of weight loss and the temperature of maximum rate of decomposition, given by the maximum in the derivative. Additionally the amount of weight loss at that temperature (T, ( _0nse t) ) was determined (AW). All these parameters are included in Table 3.

The polymer produced in Comparative Example 6 had lower degradation temperatures (Ti, T(5) and Ti(onset)) and higher weight loss than that obtained in Example 8.

TABLE 3

The results of the static thermal stability test are shown in Fig. 4. It can be seen that bubbles appear in Comparative Example 6 (presumably due to the earlier formation of butyl chloride), which will limit dramatically the potential applicability of the material; whereas the product obtained in Example 8 is free of this problem.

The lower thermal stability either limits the applicability of the polymer or involves the need to use additional dosage of additives in order to avoid formation of bubbles.

The above-mentioned assays demonstrate the higher thermal stability of the polymer of the invention. COMPARATIVE EXAMPLE 1 1 - Molecular weight distribution

The polymerization procedure carried out in Comparative Example 6 was a single-electron-transfer/degenerative-transfer-mediated "living" polymerization that yielded a narrow molecular weight distribution (polydispersity index (Mw/Mn, where Mn is the number average molecular weight and Mw is the weight average molecular weight) determined from the molecular weight distribution (Fig. 5) was 1 .7).

In contrast, the procedure carried out in Example 8 used thermal or redox initiators that produced a conventional radical polymerization in which a broader molecular weight distribution was obtained (polydispersity index determined from the molecular weight distribution (Fig. 5) is 2.9). REFERENCES CITED IN THE APPLICATION

1 . US 20090143547

2. US 41 18440

3. JM Goldwasser and A Rudin, "Emulsion copolymerization of styrene and methyl methacrylate", J. Polym. Sci. Polym. Chem. ED., 1982, Vol. 20, p.

1993

4. A Urretabizkaia, et al. "Calorimetric monitoring of emulsion copolymerization reactions", J. Polym. Sci. Part A: Polym. Chem., 1994; Vol. 32, p. 1761

CLAUSES

1 . A process for the preparation of a polymer from at least one monomer A which is a vinyl halide monomer and at least one monomer B either by redox or thermal free radical polymerization in aqueous medium, wherein the at least one monomer B is present in the polymer in an amount of up to 25 wt% of the total monomers in the polymer, being the sum of the at least one monomer B and the at least one vinyl halide monomer in the polymer of 100 wt%, the process comprising the following steps: a) mixing water, at least one amphiphilic substance, and optionally a buffer, a specific amount of the at least one monomer B, and a specific amount of the the at least one monomer A at an appropriate temperature to carry out the polymerization, wherein the amount of the at least one monomer B is from 30 to 100 wt% of the total amount of monomer B and the amount of the at least one monomer A is of from 10 to 100 wt% of the total amount of monomer A, and adding either a redox or a thermal initiator in order to start polymerization and allowing the system to react until reaching a conversion from 10 to 99 mol% of monomers, provided that when the amount of any of the monomer B or of the monomer A in step a) is less than 100 wt%, the process comprises: b) adding the remaining amount of monomer A and the remaining amount of monomer B, optionally, an additional amount of the amphiphilic substance, optionally, an additional amount of the initiator, and optionally, a buffer, and allowing the mixture to react; wherein once finished the polymerization reaction of step a) or of step b), the conversion of the monomers is higher than 70%, provided that monomer B is other than a methacrylate monomer.

2. The process according to clause 1 , wherein the addition of the remaining amount of either monomer A or monomer B during step b) is made in one injection.

3. The process according to any one of clauses 1 or 2, wherein the monomer B is selected from the group consisting of an acrylate, vinyl benzoate, isobutylene, dialkyl maleate, di-alkyl fumarate, vinyl decanoate and its isomers, vinyl esters of versatic acid including VeoVa monomers, and vinyl acetate.

4. The process according to clause 3, wherein the monomer B is an acrylate.

5. The process according to any one of clauses 1 to 4, wherein the amount of the monomer B of the total amount of monomers in the polymer is from 3 to 10 wt%. 6. The process according to any one of clauses 1 to 4, wherein the amount of the monomer B of the total monomers in the polymer is from 10 to 25 wt%.

7. The process according to any one of clauses 1 to 7, wherein monomer A in step b) is added in one or more injections.

8. The process according to any one of clauses 1 to 7, wherein monomer B in step b) is added in one or more injections.

9. The process according to any one of clauses 1 to 8, wherein in step a) the polymerization reaction is carried out by mixing from 30 to 100 wt%, from 50 to 100 wt%, or from 60 to 100 wt%, of the total amount of the at least one monomer B; and from 30 to 100 wt%, from 50 to 100 wt%, or from 60 to 100 wt%, of the total amount of the at least one monomer A.

10. The process according to any one of clauses 1 to 6, wherein in step a) the polymerization reaction is carried out by mixing the 100 wt% of the at least one monomer B, and the 100 wt% of the at least one monomer A, and the mixture is allowed to react until the conversion of the monomers reaches a value higher than higher than 70 wt%. 1 1 . The process according to any one of clauses 1 -10, wherein the polymerization is carried out in aqueous suspension.

12. The process according to any one of clauses 1 -1 1 , wherein the vinyl halide monomer is vinyl chloride.

13. A polymer obtainable by the process of any one of clauses 1 -12.

14. An article of manufacture made of the polymer of clause 13.