A LUBRICANT ADDITIVE

TECHNICAL FIELD

The present invention relates to additives which have inner lubrication characteristics for use in plastic sector.

The present invention particularly relates to an inner lubricant additive which is for use in PVC applications and which does not include phthalate.

KNOWN STATE OF THE ART

PVC is substantially viscose in molten form, and is inclined to adhere to metal components of processing equipment. This problem can be overcome by using lubricants. The basic function of lubricants in rigid PVC (rPVC) and other polymers is to decrease inner and external friction. Thus, at lower temperatures, advantages like easiness in flow, reduction in degradation probability of polymer, increase in production ratio, reduction in abrasion of equipment, less energy consumption are obtained.

Lubricants are essentially classified as inner or external. Even though both types of lubricants are mixed with PVC polymer, they realize different functions. External lubricants do not substantially dissolve in PVC. They migrate to the polymer surface when they are in molten form. They cover the metal surface of the process equipment and decrease friction on the surface and provide external lubrication. In this case, bonding force between the polymer and the lubricant is weak.

Inner lubricants are mostly dissolved in PVC. During process, inner lubricants function as included at molecular level to the movement of PVC chains. For an inner lubricant, the desired effect provides regulation of the polymer chains such that the polymer chains can be guided towards the flow direction. Thus, sliding tension between polymer molecules is decreased by the inner lubricant, and, therefore, molten viscosity and temperature increase are decreasing.

However, most lubricants have both outer and inner combinations. Dissolvability of the lubricant is essentially determined by molecular structure of polymer and by the polarity thereof. A complete dissolvability is not desired because of the risk of fragmenting of polymer between the lubricant and the polymer.

Although there are lubricant classes at a substantially wide range for rigid PVC, most of them are considered as wax or soap. The five main chemical classes are as follows: Amides; hydrocarbon waxes; oil acid esters; oil acids; metallic soaps.

There are various type ester lubricants used in various rPVC formulations: Simple esters, glycerol esters, poly-glycerol esters, montan esters, partial esters of multi-functional alcohols, completely esterificated esters of multi-functional alcohols. Except montan esters, these esters are made of various alcohols and oil acids. These lubricants are essentially named as oil acid esters. Esters are essentially versatile and the characteristics thereof can change as inner or outer lubricant by means of increasing carbon chain length and esterification degree. Therefore, lubrication characteristics of an ester can be adapted for specific applications.

Although various oil acids are commercially available, the most frequent oil acid used as a lubricant for rPVC is the mixture of palmitic (length of chain with 16 carbons) and stearic (length of chain with 18 carbons) acids. These are one each good outer lubricants besides some good lubricant characteristics. The biggest disadvantages are that they have low volatility.

As rPVC processing becomes more complex, as the proportions increase and as the parts become more complex, having better inner and outer characteristics and having better balanced lubricant systems become more critical. This condition necessitates the mixture of essentially two or more lubricants which have inner and outer lubricant characteristics. As an example to these, paraffin/oxidized polyethylene/calcium stearate, oxidized polyethylene/oil acid ester, oil acid ester mixture, paraffin/amide, etc. can be given.

Since operation of commercial scale equipment is substantially costly, the effects of a newly developed lubricant system on the rPVC compound are measured by using laboratory scale equipment like rheometer, dynamic two cylinder mills, small scale molding machines and extruders.

The material being whether inner or outer lubricant is depending on the joining ability of the material with rPVC, adhesion durations and the effects on the molten viscosity. The inner lubricants shall not seriously affect adhesion durations but shall decrease the molten viscosity. The external lubricants shall affect on the adhesion duration but shall not substantially decrease the melting viscosity. These characteristics can be measured in a torque rheometer and dynamic two-rolled mill.

The effect of lubricant systems on processing can be measured in laboratory scale extruders and injection molding machines. Hard PVC can be processed in various equipments like extruders (both single screwed and double screwed), calendering machines and injection molding machines.

The lubricant system must be balanced in terms of the requirements of processing and end usage characteristic. While single screw extruders need inner and outer lubricant balance, double screw extruders, calenders and injection molding machines need more external lubricant. Lubricant systems are not only balanced for the processing equipment, at the same time, the lubricants affect the necessary end usage characteristics in a favorable manner. A formulation optimized completely provides high output amount, low waste ratios, high quality finished products and necessary physical characteristics. Insufficient or excessive amount of lubricant leads to decrease of the processing efficiency or can even stop processing. A balanced lubricant system (the correct amounts of both the inner and outer lubricants) provides control on thermal stability durations, output ratio, blooming, transparency and physical characteristics.

In recent times, plastic products are used frequently in daily lives of all people in both developed and developing countries. Such plastic products comprise additives added intentionally for developing and improving the technical and industrial characteristics of end products. In the known state of the art, these additives are phthalic acid esters used in various products.

Plastic additives connected physically to plastic products can easily move to the surface through the polymer, moreover, they can leave the polymer and thus, they can be released to the environment. However, phthalates easily enter the environment by means of leakage, displacement and volatility during production and during usage and after disposal of the products. Phthalates have various damages for human health. For instance, high doses of phthalate change hormone levels and lead to birth faults, breast cancer, and lung and renal failures.

For these reasons, in the known state of the art, additives which do not give damage to the environment and to human health are needed. As a result, the above mentioned disadvantages and the insufficiency of the present solutions made it necessary to make an improvement in the related technical field.

BRIEF DESCRIPTION OF THE INVENTION

The present invention relates to an inner lubricant additive, a process for preparing said inner lubricant additive, a PVC composition including said inner lubricant additive and a process for preparing said PVC composition, for meeting the abovementioned requirements and for eliminating the abovementioned disadvantages and for bringing new advantages to the related technical field.

The primary object of the present invention is to obtain an inner lubricant additive which does not include chemical substances like distearyl phthalate which gives damage to human health or to the environment. Particularly, the object of the present invention is to obtain an additive which has function as inner lubricant in rigid PVC process.

Another object of the present invention is to obtain an inner lubricant additive which increases processability performance of PVC compositions.

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is an inner lubricant additive for use in shaping plastics, and it comprises distearyl adipat.

In a preferred embodiment of the present invention, said inner lubricant additive essentially does not include phthalate.

In a preferred embodiment of the present invention, said distearyl adipat is obtained by entering stearyl alcohol and adipic acid to esterification reaction.

In another preferred embodiment of the present invention, the stochiometric proportion of stearyl alcohol and adipic acid in esterification reaction is 2-2.5:1 .

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a process for preparation of an inner lubricant additive for use in shaping plastics, and said process comprises the step of entering stearyl alcohol and adipic acid to esterification reaction. In a preferred embodiment of the present invention, said process essentially does not include entering of an alcohol and phthalic anhydrite to esterification reaction.

In another preferred embodiment of the present invention, the stochiometric proportion of stearyl alcohol and adipic acid in esterification reaction is 2-2.5:1 .

In another preferred embodiment of the present invention, said esterification reaction is realized in the presence of acid catalyst.

In another preferred embodiment of the present invention, said process comprises the step of grinding and powdering of distearyl adipat mixture obtained as a result of esterification reaction.

In another preferred embodiment of the present invention, said process comprises the step of adding at least one agglomeration preventing additive to the distearyl adipat mixture, obtained as a result of esterification reaction, before grinding.

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a method for production of an inner lubricant additive for use in shaping plastics, said method comprising the steps of:

- obtaining distearyl adipat;

- obtaining at least one agglomeration preventing additive;

- turning said agglomeration preventing additive into a mixture by means of distearyl adipat; and

- grinding the mixture obtained in the step iii) and turning the mixture into powder form.

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a PVC composition and it comprises distearyl adipat as the inner lubricant.

In a preferred embodiment of the present invention, said PVC composition essentially does not include phthalate.

In another preferred embodiment of the present invention, said distearyl adipat is obtained by entering stearyl alcohol and adipic acid to esterification reaction. In another preferred embodiment of the present invention, the stochiometric proportion of stearyl alcohol and adipic acid in esterification reaction is 2-2.5:1 .

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a process for preparation of a PVC composition comprising at least one inner lubricant, and comprises the step of entering stearyl alcohol and adipic acid to esterification reaction.

In a preferred embodiment of the present invention, said process essentially does not include the step of entering an alcohol and phthalic anhydrite to esterification reaction.

In a preferred embodiment of the present invention, the stochiometric proportion of stearyl alcohol and adipic acid in esterification reaction is 2-2.5:1.

In a preferred embodiment of the present invention, said esterification reaction is realized in the presence of acid catalyst.

In a preferred embodiment of the present invention, said process comprises the step of grinding and powdering of distearyl adipat mixture obtained as a result of esterification reaction.

In a preferred embodiment of the present invention, said process comprises the step of adding at least one agglomeration preventing additive to the distearyl adipat mixture, obtained as a result of esterification reaction, before grinding.

In order to realize the abovementioned objects and the objects which are to be deducted from the detailed description below, the present invention is a method for production of a PVC composition comprising at least one inner lubricant, said method comprising the steps of:

- obtaining an inner lubricant additive including distearyl adipat;

- obtaining at least one agglomeration preventing additive;

- turning said agglomeration preventing additive into a mixture by means of distearyl adipat;

- grinding the mixture obtained in the step iii) and turning the mixture into powder form; and

- obtaining the additive, which is in powder form, to a PVC mixture; and

- adding said inner lubricant additive to PVC mixture. The structural and characteristic properties and all advantages of the present invention will be understood in a more clear manner by means of the below mentioned figures and the detailed description written by making reference to these figures, therefore, evaluation shall be made by taking into consideration these figures and the detailed description.

DETAILED DESCRIPTION OF THE INVENTION

In this detailed description, an inner lubricant composition which is suitable for use in plastic formulations, particularly in PVC formulations and a process for preparation of this composition are described. The preferred embodiments of the present invention are explained with references to examples without forming any restrictive effect only in order to make the subject more understandable.

In the present application, the inner lubricant additive means an additive which decreases friction between polymer-polymer, polymer-metal or polymer-filler.

The present invention describes an inner lubricant additive for use in shaping plastics. Said inner lubricant additive comprises distearyl adipat. The chemical structure of distearyl adipat is shown by Figure 1.

Figure 1

Distearyl adipat is preferably obtained by means of esterification reaction of stearyl alcohol and adipic acid in the presence of acid catalyst.

Esterification reaction can be realized by using a known method by a person who is skilled in the known state of the art.

The desired distearyl adipat is obtained by means of esterification of stearyl alcohol and adipic acid with proportion of 2-2.5:1 , preferably proportions of 2:1 or 2.5:1.

In another preferred embodiment of the invention, the inner lubricant additive essentially does not include a phthalate including distearyl phthalate. By means of this, as the inner lubricant, a new inner additive is presented which does not comprise phthalate, in other words, which does not comprise chemical substances which give damage to human health or to the environment. Moreover, by means of the invention, it has been found that said additive has the same PVC processing performance when compared with the alternatives including phthalate or increases this performance and provides improvements in gelling time and torque values and does not lead to color deteriorations.

In the known state of the art, phthalate is obtained by means of esterification reaction of an alcohol component, for instance, methanol, ethanol, penta-eritritol, tris-methylol-propane (TMP), sorbitol, glycerol, diglycerol, poly-glycerol or and phthalic anhydrite which gives damages to human health and to the environment. Thanks to the present invention, adipic acid, which is a dicarboxylic acid, can be used instead of phthalic anhydride in preparation of the inner lubricant additive. Thus, the usage of phthalic anhydrite is prevented, and at the same time, phthalic anhydrite residues in the end product are prevented.

Here, the statement “does not essentially include phthalate” means that the inner lubricant additive does not include any phthalate or that the inner lubricant additive comprises phthalate at a low level which does not give damage to human health or to environment. It is considered that phthalate with proportion of 0.1% by total weight does not give damage to human health and environment health. Accordingly, in the present invention, the statement “does not essentially include phthalate” has been used in the meaning of “including phthalate with proportion between 0% and 0.1% by total weight”. Said phthalate can be distearyl phthalate. The chemical structure of distearyl phthalate is shown by Figure 2.

Figure 2

The present invention describes a process for preparation of an inner lubricant additive for use in shaping plastics. Said process comprises the step of entering stearyl alcohol and adipic acid to esterification reaction. It has been found that distearyl adipat, obtained by means of said esterification reaction, has inner lubricant characteristics particularly in PVC compositions and has the same PVC processing performance when compared with phthalates or increases this performance.

In a preferred embodiment of the invention, said process essentially does not include the step of entering stearyl alcohol and phthalic anhydrite to esterification reaction. By means of this, the usage of phthalic anhydrite, which is harmful for the human health and environment, is avoided and the desired inner lubricant performance is also obtained.

Here, the statement “essentially does not include the step of entering stearyl alcohol and phthalic anhydrite to esterification reaction” means that the inner lubricant additive, obtained by means of said process, does not include any phthalate or comprises low level of phthalate which does not give damage to human health or to environment. It is evaluated that phthalate, which has proportions lower than 0.1% by total weight, does not give damage to human and environment health. Accordingly, in the present invention, the statement “does not essentially include phthalate” has been used in the meaning of including phthalate at a proportion between 0% and 0.1% by total weight.

In the subject matter process, in the esterification reaction, the proportion of stearyl alcohol and adipic acid is equal to 2-2.5:1 , preferably equal to 2:1 or 2.5:1 . Esterification is preferably realized in the presence of acid catalyst.

The subject matter process moreover can comprise the step of grinding of distearyl adipat mixture obtained as a result of esterification reaction and turning said distearyl adipat mixture into a form with powder, flake or lentil size.

For providing this, at least one agglomeration preventing additive can be added before grinding to the distearyl adipat mixture obtained as a result of esterification reaction. The agglomeration preventing additive is added into the reaction medium during cooling preferably after the esterification reaction is completed.

The agglomeration preventing additives are inert organic or inorganic compounds which decrease probability of attraction between particles in some products (food, drug, dye, cosmetic, etc.) which are in powder form and which prevent adhesion and which provide fluidity of products which are in powder form or which have tiny particles and which prevent agglomeration probabilities. Such materials are called “agglomeration preventing agent”, “adhesion preventing agent”, “free flow agent” or “drying agent” in the literature. Said materials, which cover the particles with a thin layer, increase the distance between the particles and prevent the electrostatic attraction between the oppositely charged particles and prevent adhesion of particles to each other. The agglomeration preventing additives, which can be used in the present invention, are materials already used at important proportions as stabilizer or filler in plastic, particularly in PVC compositions. Since said agglomeration preventing additives are used in plastic formulations, they are useful in turning the inner lubricant additive into powder form and prevent caking and petrification, and the additional usage of said filling materials or stabilizers during processing of a plastic material is prevented. Fillers are materials which cheapen the product and which provide toughness. Among the fillers which can be used as the agglomeration preventing additive which is compliant to the present invention, there are calcium stearate, magnesium stearate, calcite (calcium carbonate) and talc (magnesium hydro-silicate) without limitation with these. Among the stabilizers which can be used as the agglomeration preventing additive which is compliant to the present invention, there are calcium-based stabilizers, organo-tin-based stabilizers, metal stabilizers. Among the grinding systems which can be used in the subject matter process, there are mill types like razor grinding mills, geared grinding mills and sprayed cooling systems without limitation.

The present invention moreover describes a method for production of an inner lubricant additive for use in shaping plastics. Said method comprises the steps of: i) obtaining distearyl adipat; ii) obtaining at least one agglomeration preventing additive; iii) turning said agglomeration preventing additive into a mixture by means of distearyl adipat; and iv) grinding the mixture obtained in the step iii) and turning the mixture into powder form.

The subject matter inner lubricant additives are used in polymer shaping processes which show plastic characteristic. Said inner lubricant additive is particularly suitable for shaping polyvinyl chloride (PVC) like rigid PVC, polymers with chlorine like poly-vinylidene chloride, and the copolymers which are the derivative thereof. Moreover, said inner lubricant additive can be used as process additive for engineering plastics, as mold separator and in processing PMMA (Poly(methyl)methacrylate).

The subject matter inner lubricant additive can be added to plastic, for instance, to hard or soft PVC mixtures with changing proportions. The subject matter inner lubricant additive is added to the plastic material, which is to be processed, before processing. The amount of the added inner lubricant additive depends on the plastic material to be processed and the processing type. The present invention describes a PVC composition which comprises distearyl adipat as inner lubricant and PVC polymer. PVC composition comprises inner lubricant additive with proportion between 0.2% and 0.6% by total weight. By using these proportions, the desired physical and mechanical characteristics in the end product are obtained.

PVC composition can comprise other additives like stabilizers (for instance, lead salts, calcium-zinc), fillers (for instance, calcium carbonate), dyes (for instance, titanium dioxide), process adjuvant agents (for instance, acrylic-based adjuvant agents), impact additives (for instance, chlorinated PE, methyl-butadiene-sitren and acrylonitrile-butadiene-sitren).

In a preferred embodiment of the present invention, PVC composition does not include distearyl phthalate.

In another preferred embodiment of the present invention, PVC composition essentially does not include a phthalate including distearyl phthalate. By means of this, a new PVC composition which does not include phthalate is presented as the inner lubricant. It has been found that the subject matter PVC composition has the same PVC processing performance when compared with alternatives comprising phthalate or increases this performance. During processing, the power (torque value) applied by the device decreases and the color of the end product is not affected unfavorably.

EXAMPLES

Example 1 - Preparation of PVC compositions which include inner lubricant additive

Table 1 - Content of the composition with phthalate Table 2 - Content of the composition with adipat

The components, given in Table 1 and Table 2, are mixed in a mixer until a homogenous mixture is obtained as separate pre-processes. The mixer temperature is controlled and excessive heating is taken under control for non-degradation of PVC (PVC begins to degrade after 120 ^e C). After the mixture is provided, the mixture is fed to the extruder system, and the end product is removed from the extrusion system.

Example 2 - Specifications

The specification values expected from the product and the analysis results which belong to the obtained products are given in Table 3.

Example 3 - Performance comparisons Plastograph results:

Color Measurements:

Congo red test: This test method aims at determining thermal stability of a PVC compound when said PVC compounds are processed at a high temperature. The method can be applied to all PVC compounds, copolymers and products dependent on these. A test sample of PVC material is heated to a specific temperature which is normally between 180-200 ^e C. The duration which passes for the degradation of the material because of hydrogen chloride is determined by a color change on Congo red test paper.

When PVC products comprising adipat and phthalate are compared, they show similar thermal stability within the same duration (100 minutes) at 200 ^e C.