BHAR RIMITA (IN)
KHILARE MAHESH (IN)
GOEL RAJEEV KUMAR (IN)
SATHEESH KUMAR M. N., YAAKOB Z., SIDDARAMAIAH: "Poly(styrene-co-butyl acrylate) Latex-Reinforced Polyester Nonwoven Fabric Composites: Thermal and Morphological Studies", JOURNAL OF APPLIED POLYMER SCIENCE, vol. 114, no. 1, 8 June 2009 (2009-06-08), pages 467 - 474, XP055767182, DOI: 10.1002/app.30518
KUMAR M. N. SATHEESH, SIDDARAMAIAH: "Studies on Cornstarch-filled Poly(styrene-co-butyl acrylate) Latex-reinforced Polyester Nonwoven Fabric Composites", JOURNAL OF REINFORCED PLASTICS AND COMPOSITES, vol. 24, no. 18, 1 December 2005 (2005-12-01), pages 1985 - 1994, XP055767183, DOI: 10.1177/0731684405054379
| WE CLAIM: 1. Biopolymer based copolymer emulsion comprising biopolymer doped acrylic latex including copolymer of monomers including styrene and butyl acrylate onto non-degraded, non-gelatinized polysaccharide that is a stable flowable polymer dispersion having solid content in the range of 30-50% by wt. free of any phase separation, viscosity increase and gelation upon storage. 2. Biopolymer based copolymer emulsion as claimed in claim 1 wherein said polysaccharide as a secondary binding agent is a non-ionic, non-degraded, non- gelatinized starch, dextrin, maltodextrin, preferably non-degraded, non- gelatinized tapioca starch. 3. Biopolymer based copolymer emulsion as claimed in claims 1 or 2 wherein said emulsion comprises acrylic polymer with polysaccharide incorporation in the levels of 3% to 10% in said acrylic polymer that is a low molecular wt. polysaccharide having mol. wt. in the range of 100-5000g/mol. 4. Biopolymer based copolymer emulsion as claimed in claims 1-3 wherein said emulsion comprising acrylic polymer includes a monomer ratio of styrene: butyl acrylate in the ratio range of above 50:50 to below 70:30, preferably 55:45 having Tg in the range of 5-20 °C. 5. Biopolymer based copolymer emulsion as claimed in claims 1-4 comprising monomers including methyl methacrylate, ethyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, styrene, acrylic acid, methacrylic acid, hydroxyl ethyl methacrylate, hydroxyl propyl methacrylate free of monomers including isobornyl methacrylate, isobornyl acrylate, C18 PEG methacrylate, amino methacrylates, benzyl methacrylate, VAM monomer, present together with surfactants, and non-polymerizable crosslinkers. 6. Biopolymer based copolymer emulsion as claimed in claims 1-5 wherein said surfactant/emulsifiers is selected from anionics including Polyoxyethylene alkyl ether sulfate, Alkyl sulfate, Alkyl benzene sulfonate; nonionics including polyoxyethylene alkyl ether, Polyoxyalkylene fatty alcohol, Sorbitan fatty acid esters stabilizing the emulsion for at least 1 year in viscosity range of 50-100g. 7. Biopolymer based copolymer emulsionas claimed in claims 1-6 wherein said biopolymer doped acrylic latex comprises fine particle aggregates including said copolymer of styrene, butyl acrylate including unsaturated carboxylic acid, onto polysaccharides, as biopolymer that exist homogeneously in each aggregate particle having diameter in the range of 100 to 200 nm for sufficient desired opacity and strength and adhesion in terms of washability and scrub resistance, adapted for anyone of high PVC emulsion paint with reduced inorganic pigment, binder for concrete coating, having the characteristics improved opacity and reduced strength, better coverage and ease of application in concrete coatings based on the involvement of said lowmolecular weight nonionic polysaccharide/sta rch. 8. A process for the synthesis of biopolymer based copolymer emulsion comprising sequential seeded multi stage free-radical aqueous polymerization of monomers including styrene and butyl acrylate as essential monomers in the presence of non-degraded, non-gelatinized polysaccharide and obtaining therefrom biopolymer doped acrylic latex including copolymer of styrene and butyl acrylate onto non-degraded, non-gelatinized polysaccharide as a stable flowable polymer dispersion having solid content in the range of 30-50% by wt. free of any phase separation, viscosity increase and gelation upon storage. 9. The process as claimed in claim 8 comprising the steps of Preparing aqueous polymer dispersion comprising monomers including styrene and butyl acrylate as essential monomers taken in the ratio range of styrene: butyl acrylate in the ratio range of above 50: 50 to below 70:30, preferably 55:45, and polymerizing said monomers by free radical aqueous polymerization in the presence of non-degraded, non-gelatinized polysaccharide preferably tapioca dextrin at emulsion polymerization temperature of 65 to 95°C, preferably from 75 to 85°C. 10. The process as claimed in claims 8 or 9 wherein said monomer as 100 parts by weight monomer or mixed monomer comprises 0 to 70% by weight of vinyl aromatic monomer, 0 to 50 % by weight of an ethylenically unsaturated monomer together with unsaturated carboxylic acid selected from unsaturated monobasic acids such as methacrylic acid and acrylic acid preferably acrylic acid in an amount of 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of total monomers making up said copolymer, which said monomers are polymerized in a sequential seeded multistage semi-continuous process in presence of 3 to 10 % by weight dextrins free of any derivatization, gelantization and thinning. 11. The process as claimed in claims 8-10 comprising the steps of Charging entire amount of said dextrinas aqueous solution into the polymerization reactor followed by surface active agents/emulsifierswith intense and homogeneous mixing prior to addition of emulsified monomer mixture, with initial solid content kept at 15 to 20% by weight, for seeding; Carrying out free-radical aqueous emulsion polymerizationeither as a batch process or as feed process, preferably feed process in presence of polymerization initiators wherein part of the polymerization batch is heated to said polymerization temperature and partially polymerized, followed by feeding the remainder of the polymerization batch to the polymerization zone continuously, preferably via separate feed streamssaid separate feed streams enabling feeding said monomers frequently to the polymerization zone post pre-emulsification with surface active agents/emulsifiers to favour reduced surface tension and simplify stirring and comprises two stages : Wherein in the first stage emulsified monomer mixture and catalyst are fed into the polymerization reactor over a period of 45 to 75 minutes while maintaining the polymerization temperature. Wherein in the second stage polymerization is carried out by adding additional emulsified monomers and catalyst mixture to the dextrin polymer dispersion in the polymerization reactor for about 150 to 180 minutes. 12. The process as claimed in claims 8-11 wherein said polymerization initiators include persulfatesof potassium persulfate, sodium persulfate and ammonium persulfate; organic peroxides such benzoyl hydroperoxide, redox initiators by combining them with a reducing agent such as sodium formaldehyde sulphoxalate; and wherein said surface active agent is includes anionic surface active agent, a nonionic surface active agent or a combination thereof includinganionic surface active agent comprising sodium alkylsulfate, sodium dialkylsulfosuccinate, nonionic surface active agents including polyoxyethylene alkyl ether and polyoxyethylenealkylphenol ether in amounts of 0.5 to 5 parts by weight per 100 parts by weight of all monomers. 13. The process as claimed in claims 8-12 providing for biopolymer doped acrylic latex comprising fine particle aggregates of biopolymer doped acrylic latex onto polysaccharides obtained of a mixture including styrene, butyl acrylate, unsaturated carboxylic acid and said biopolymer wherein said biopolymer exist homogeneously in each aggregate particle having diameter in the range of 100 to 200 nm for sufficient desired opacity and strength and adhesion in terms of washability and scrub resistance. |
POLYSACCHARIDE-BASED COPOLYMER FOR SURFACE COATING
FIELD OF INVENTION
The present invention provides for biopolymer based copolymer emulsion comprising biopolymer doped acrylic latex including copolymers of monomers including styrene and butyl acrylate onto non-degraded, non-gelatinized polysaccharide, including starch/dextrin at low dosage, together with the synthetic monomers in select amounts, thus providing for biopolymer based/doped copolymer, preferably biopolymer doped styrene acrylic latex and emulsions thereof suitable for concrete coating compositions/ high PVC decorative paints, and advantageously having improved opacity and reduced strength, better coverage and ease of application as concrete coatings.
BACKGROUND ART
Acrylic latex doped with biopolymers such as starch, modified starch such as dextrin and maltodextrin improves its properties and create bio-friendly, naturally degrading material, diminishing negative effect of biopolymer. Use of biopolymers in polymer synthesis has been reported in various fields like, paper coating, adhesive, medical industry. However, often this starch or dextrin derived from corn, waxy corn, red milo, white milo, wheat, potato and tapioca, is gelatinized with enzyme or persulfate salt before reaction in order to achieve stable viscosity and acts as protective colloid. Unmodified dextrin/starch has limited application in coating industry. Cationic starch has also been used in paper and board coating. Prior art reveals the deficiency of use of unmodified starch/dextrin in small quantity that is used in decorative coating formulation as a sole binder system.
Reference is invited to WO2015160794 that teaches bio-based nanoparticle and composite materials thereof disclosing preparation of a crosslinked nanoparticle comprising a bio-based compound and monomer, oligomer, macromer, and polymer by reactive extrusion process. Here biopolymers are functionalized to provide double bond or free radical. The prepared nanoparticle is further copolymerized with vinyl monomer forms a bio-synthetic hybrid latex particles as a whole are rendered biodegradable.
WO2015084372 is directed to a formaldehyde-free or formaldehyde-reduced binders useful, for example, in a fiber based composite material such as glass or other mineral fiber
insulation, non-woven fabric or wood-based board. In one example, melamine is used as
an acidic solution or a salt. The salt or solution is used to create an aqueous binder withother components such as a polyol and a crosslinker. A preferred polyol is a nanoparticle comprising high molecular weight starch. In other examples, binders include mixtures of a polyolwith urea and a crosslinker. In other examples, a multi-component nanoparticle is madeby reacting a polyol such as starch in an extruder with an insolubilizer such as melamineor urea. The resulting particles are mixed with water, optionally with other componentssuch as an additional crosslinker, to create an aqueous binder. The binders to be blended with a conventional latexbinder, such as polystyreneacrylate is also stated. Thus this patent is effect describes the blended composition (not achieved by synthesis) wherein a resin is first prepared by dispersing polyol (starch), crosslinkers such as glyoxal, citric acid, melamine, urea, reactive amine dissolved in water to form a colloid forming particle, which colloidal solution is suitable for blending with conventional latex such as SA, SB, and PVA for intended application.
W02018010094 teaches a cosmetic pickering emulsion composition comprising adispersed fatty phase, and a continuous aqueous phase, and consisting of a hydrophobic gelling agent selected from ester of dextrin and fatty acid, an amphiphilic crosslinked copolymer, an anionic terpolymer, linear or branched together with hydrophobic particles chosen from hydrophobic silica and cellulose, starch, talc, silicone resin powders, hollow hemispherical silicone particles, polyamide powder, hydrophobic pigments. This prior patent in effect thus discloses a cosmetic composition prepared by using an ester of dextrin and fatty acid, an amphiphilic acrylic copolymer, a terpolymer containing acrylic crosslinkers, hydrophobic silica and cellulose, starch, talc, silicone resin powders, hollow hemispherical silicone particles, polyamide powders and hydrophobic pigments. The composition is a cosmetic pickering emulsion which is surfactant free and includes dextrin as an additive and not a binding agent. KR2010002101A teaches organic/inorganic composite composition containing aerogel for heatinsulating coating and manufacture of molded sheet and though involves starch and other inorganic materials and a polymer present inthe composition possibly as an admixture wherein the polymer is a water absorbing polymer.
CN108102544A teaches environmental-friendly interior wall emulsion paint that includes the following raw materials: 55-65 parts of modified defatted soy bean paste, 35-45 parts of vinyl acetate/acrylic emulsion, 25-30 parts of starch, 20-25 parts of Portland cement, 15-20 parts of modified wood fiber, and 15-20 parts of propolis powder, 10-15 parts of zeolite, 10-15 parts of KM5 nanoparticles, 5-10 parts of modifiedexpandable graphite, 5-10 parts of extinction powder, 5-10 parts of water-soluble dextran, 20-25 parts of auxiliaries, and 75-95 parts of water. The auxiliaries include the following parts of the raw materials: 4-6 parts of colorant, 2-3 parts of leveling agent, 2-3parts of water retaining agent, 1-2 parts of dispersant, 1-2 parts of defoamer, 1-2 partsof plasticizer, 0.8-1.2 parts of antioxidant and 0.6-0.8 parts of mildew inhibitor. The interior wall emulsion paint enhances smoothness, good antibacterial effect, easyscrubbing, and safety and environmental protection. Teaches the employment of dextrin as an additive and not a monomer substitute to lead to a dextrin modified latex. CN106221332 teaches following raw material: butadiene-styrene emulsion, siliconeacrylicemulsion, nano-titanium oxide concentrated pulp, Bu acrylate, Me methacrylate, ultra-fine wollastonite, titanium dioxide, diatomite, white cement, mung bean modifiedstarch, boron fiber, polyester fiber, hydroxypropyl Me cellulose, glycerol, sodium etc. Thus teaches a paint formulation which involves butadiene-styrene or silicone-acrylic emulsion and a method of making latex paint by incorporation various ingredients such as monomers, emulsions, inorganic materials, surfactant, dispersing agents, catalyst, starch etc. but does not teach any dextrin modified latex.
CN 106147330A teaches environmentally friendly emulsion paint, comprising the following raw materials: vinyl acetate-maleic anhydride emulsion 28-40, styrene- acrylate copolymer emulsion 22-35, nano-titanium oxide concentrated pulp 18-25, Bu acrylate 12-16, Me methacrylate 8-12, ultra-fine wollastonite 7- 10, titanium dioxide 4-6, atlapulgite 5-8, white cement 6-9, cassava modified starch 10-17, boron fiber 2-4, polyester fiber 3-6, hydroxypropyl methylcellulose 4-8, glycerol 15-19, dispersing agent NC 1-2, sodium dodecylbenzenesulfonate 0.5-0.8, stearic acid 0.4-0.6, leveling agent DSX2000 0.3-0.6, wetting agent CF- 10 0.2-0.4, colorless cobalt 0.3-0.5, Pt catalyst 0.1-0.2, polyurethane thickener
SN636 0.3-0.6 part by wt. The environmentally friendly emulsion paint of the present invention has high vol. solid content, and can increase paint film thickness, and protect wall surface effectively, and the paint film has strong adhesion, and excellent water tolerance, and alkaline resistance, belonging to low carbon product, and meeting national energy-saving and emission-reduction policy. While the ingredient starch finds mention that is only blended with the latex emulsion does not teach any dextrin modified latex.
CN 106147331A similarly teaches preparation method of high performance latex paint that includes mixing, dispersing, sand milling, stirring, adjustingpH, and microwave stirring. The high-performance latex paint contains: butadienestyreneemulsion30-38,acrylateemulsion24-
33,nanotitaniumoxideThickenedpulp2024,Bu acrylate 12-16, Me methacrylate 8- 12, ultra-fine wollastonite 7-10, titaniumdioxide 4-6, montmorillonite 5-8, white cement 6-9, modified potato starch 10-17, boronfiber 2-4, polyester fiber 3-6, hydroxypropyl Me cellulose 4-8, glycerol 15-19, dispersingagent NC 1-2, sodium dodecylbenzenesulfonate 0.5-0.8, stearic acid 0.4-0.6, levelingagent DSX2000 0.3-0.6, wetting agent CF-10 0.2-0.4, colorless cobalt 0.3-0.5, platinumcatalyst 0.1-0.2, etc. and is about the latex emulsion blended with modified tapioca starch and does not teach any dextrin as a monomer substitute to provide for dextrin modified latex.
CN106147320 provides a environment-friendly emulsion paint comprising the following rawmaterials: vinyl acetate-maleic anhydride emulsion, styrene-acrylic emulsion, nanotitanium oxide thickened pulp, Bu acrylate, Me methacrylate, ultra-fine wollastonite, titanium dioxide, bentonite, white cement, corn modified starch, carbon fiber, polyesterfiber, hydroxypropyl Me cellulose, glycerol, dispersing agent NC, sodiumdodecylbenzenesulfonate, stearic acid, leveling agent DSX2000, wetting agent CF-10, colorless cobalt, platinum catalyst etc. Similar to the above prior arts in involving the latex blended with corn modified starch thus does not teach any dextrin as a monomer substitute to provide for dextrin modified latex.
W02001029091A1 is directed tolow-amylose (preferably <2%) starch, preferably modified or derivatized, especially from genetically modified potatoes into which an amylose producing-inhibiting gene has been introduced, is used, optionally together with common emulsifiers or auxiliary agents, as protective colloid during emulsion [co]polymerization and for stabilizing of emulsions, which are suitable for use in the paper, adhesive, paint, or textile industries, as building materials or as coatings for orally administered active substances. Amylopectin does not tend to retrograde and is obtained at low cost by co-suppression from a potato, in which amylose formation is inhibited by antisense inhibition of a GBSS gene, so that the amylose content is <5%, especially<2%. The potato starch is degraded and used as (half) ester or ether of (in)organic acids as (hydroxy)alkyl ethers, esp. hydroxyethyl and hydroxypropyl ether, carboxyalkyl ethers, cyanoalkyl ethers, allyl ethers or (trialkylammonio)(hydroxy)alkyl ethers. Thus, in a one-pot reaction to a mixt. of 215 g oxidatively degraded amylopectin from potato starch and 500 g H 2 0, under N 2 and warmed to 85°, 0.07% a-amylase (relative to the dry starch) was added, stirred and heated to boiling for enzymic degradation. After 10 min, the amylase was deactivated by addition of glacial acetic acid, the mixture cooled to 85° and 7 g of a 1% FeS0 solution and 0.7 g of 30% H 2 0 2 were added. During 2.5 h 312 g Bu acrylate, 281 g styrene and 31.2 g methacrylic acid, pre-emulsified with 0.6 g Na dodecyl sulfate, were continuously added, as well as the initiator soln. (4 g 30% H 2 0 2 in 50 mL H 2 0, 3 h). After post-polymerization (1 h, 85°) a storage-stable polymer dispersion with 50% solids content was obtained. In this prior art derivatized starch is used as a protective colloid to stabilize the emulsion, also starch has been degraded in this prior art.
US5795928A teaches a prior process for preparing a latex system that has a tendency to flocculate because of grafting, the improvement comprises aqueous emulsion polymerization of >1 unsaturated monomer (e.g., acrylic acid, methacrylic acid, Bu acrylate, Me methacrylate, acrylic esters, styrene, vinyl ethers, vinyl, vinylidene halides, N-vinyl pyrrolidone, ethylene, C3 or greater alpha-olefins, allyl amines, allyl esters of saturated monocarboxylic acids and amides thereof, propylene, 1-butene, 1-pentene, 1-hexene, 1-decene, allyl amines, allyl acetate, allyl propionate, allyl lactate and derivatives) in the presence of a water-soluble protective colloid. The protective colloid has a wt.- av. mol. wt. <75,000, and is selected from CM-cellulose and derivatives having a carboxyl degree of substitution lower limit of about 0.7, hydroxyethylcellulose, Et hydroxyethylcellulose, methylcellulose, Me hydroxypropylcellulose, hydroxypropylcellulose, poly(acrylic acid) and alkali metal salts thereof, ethoxylated starch derivatives, sodium and other alkali metal polyacrylates, water soluble starch glue, gelatin, water soluble alginates, casein, agar, natural and synthetic gums, partially and fully hydrolyzed poly(vinyl alcohol), polyacrylamide, poly(vinyl pyrrolidone), poly(Me vinyl ether-maleic anhydride), gelatin, and casein. The latex has improved mechanical and shear stability. This latex provides coating manufacturers the flexibility of either eliminating surfactants altogether from coating or to use small amounts thereof. In this prior art cellulose ether acts as protective colloid and can replace surfactants fully or partially, starch is used as an additive and in a derivatized form.
EP343833A2 emulsion comprises particles (0.2-3.0 pm) of 0.5-90 parts 1- 50: 50-99 unsaturated carboxylic acid-vinyl compound copolymer (A) and 99.5- 10 parts another vinyl compound copolymer (B) (0.05-0.5 pm), wherein copolymer B is prepared in the presence of neutralized copolymer A seed particles. Emulsion polymerization Me methacrylate 4, Bu acrylate 4, and methacrylic acid 2 parts at 70° for 2 h in the presence of K 2 S 2 0 8 , neutralizing with 28% aqueous NH 3 solution to give swollen seed particles, adding styrene 85, divinylbenzene 5, H 2 0 50, and Na lauryl sulfate 0.5 parts over a 4 h period, and polymerizing 3 h gave aggregate emulsion particles (diam. 0.9 pm). Coating paper with compositions containing the above filler 10, kaolin (UW-90) 90, Aron T-40 0.09, MS-4600 (phosphated starch binder) 3, and SBR latex (Polylac 755) 12 parts at dry pickup 14-15 g/m 2 and drying at 120° for 20 s gave coated paper having color viscosity 1830 cP, 75° gloss 76.9, printed gloss (JIS P-8142) 93.0, brightness 80.5, and opacity 95.9, vs. 1370, 75.2, 90.2, 79.1, and 94.1, resp., without preparing the aggregate particles in the presence of neutralized seed particles. This prior art uses phosphated starch binder and not dextrin as a raw material during emulsion synthesis.
Thus while it is a prevalent knowledge in the prior known teaching on emulsions to involve starch as an additive in a form that is derivatized, degraded or gelatinized, so far none is found to explore the employment of starch/dextrin and in a form as found in its native state free of any degradation or gelatinization at low dosage applicable as a secondary binding agent, serving as an alternate to monomers and to be compatible with other synthetic monomers, to provide for starch/ dextrin modified latex especially suitable for paints including high PVC (pigment volume concentration) emulsion paint which is the target of the present invention.
OBJECTS OF THE INVENTION
It is thus the primary object of the present invention to provide for a biopolymer based copolymer including starch/ dextrin, which biopolymer would act as a secondary binding agent that would provide for starch/ dextrin modified latex especially suitable for paints including high PVC (pigment volume concentration) emulsion paint. It is another object of the present invention to provide for said biopolymer based copolymer preferably of select synthetic monomers of styrene and butyl acrylate onto starch/dextrin, which starch/dextrin being free of any degradation or gelatinization, derivatization, thinning taken at low dosage would be compatible with said select synthetic monomers andwould enable biopolymer/dextrin based/doped copolymer suitable for concrete coating compositions.
It is yet another object of the present invention to provide for said dextrin-based copolymer and emulsions/ coating composition thereof that would be responsible for improved opacity and reducing strength, better coverage and ease of application in concrete coatings.
It is another object of the present invention to provide for said copolymer including starch/ dextrin that is of low molecular weight and is nonionic starch (Dextrin) preferably Tapioca starch being free of any derivatization, gelantisation and thinning and yet would facilitate said copolymer emulsion. It is still another object of the present invention to provide for inexpensive polymer based copolymer emulsion which is not only renewable but also biodegradable as a replacement to synthetic monomers and 'mineral earths' material including expensive white inorganic pigments.
It is another object of the present invention to provide for a process for manufacturing said starch/ dextrin based copolymer and emulsion thereof involving select sequential polymerization process based on the incorporation of select polymer as occurring in its native state free of any derivatization, gelantisation and thinning in select amounts, together with synthetic monomers also in select amounts to thereby provide for biopolymer doped acrylic latex/biopolymer based copolymer thereof.
It is yet another object of the present invention to provide for said biopolymer based copolymer and emulsion thereof that would be suitable for use in high PVC decorative paint to have a cost-effective alternate to pure styrene acrylic backbone.
It is another object of the present invention to provide for said biopolymer based polymer and emulsion thereof that would boost a greener product and would reduce the existing scope of petroleum-based monomer content in polymer emulsion with possible reduction in inorganic pigment.
SUMMARY OF THE INVENTION
Thus according to the basic aspect of the present invention there is provided a biopolymer based copolymer emulsion comprising biopolymer doped acrylic latex including copolymer of monomers including styrene and butyl acrylate onto non- degraded, non-gelatinized polysaccharide that is a stable flowable polymer dispersion having solid content in the range of 30-50% by wt. free of any phase separation, viscosity increase and gelation upon storage. Preferably, said biopolymer based copolymer emulsion is provided wherein said polysaccharide as a secondary binding agent is a non-ionic, non-degraded, non- gelatinized starch, dextrin, maltodextrin, preferably non-degraded, non- gelatinized tapioca starch.
More preferably, said biopolymer based copolymer emulsion comprises acrylic polymer with polysaccharide incorporation in the levels of 3% to 10% in said acrylic polymer that is a low molecular wt. polysaccharide having mol. wt. in the range of 100-5000g/mol.
According to another preferred aspect of the present invention there is provided said biopolymer based copolymer emulsion wherein said emulsion comprising acrylic polymer includes a monomer ratio of styrene: butyl acrylate in the ratio range of above 50: 50 to below 70:30, preferably 55:45 having Tg in the range of 5-20 °C.
Preferably said biopolymer based copolymer emulsion comprises monomers including methyl methacrylate, ethyl methacrylate, ethyl acrylate, butyl acrylate, butyl methacrylate, styrene, acrylic acid, methacrylic acid, hydroxyl ethyl methacrylate, hydroxyl propyl methacrylate free of monomers including isobornyl methacrylate, isobornyl acrylate, C18 PEG methacrylate, amino methacrylates, benzyl methacrylate, VAM monomer, present together with surfactants, and non- polymerizable crosslinkers.
More preferably, in said biopolymer based copolymer emulsion said surfactant/emulsifiers are selected from anionics including Polyoxyethylene alkyl ether sulfate, Alkyl sulfate, Alkyl benzene sulfonate; nonionics including polyoxyethylene alkyl ether, Polyoxyalkylene fatty alcohol, Sorbitan fatty acid esters stabilizing the emulsion for at least 1 year in viscosity range of 50-100g. According to another preferred aspect of the present invention there is provided said biopolymer based copolymer emulsion wherein said biopolymer doped acrylic latex comprises fine particle aggregates including said copolymer of styrene, butyl acrylate including unsaturated carboxylic acid, onto polysaccharides, as biopolymer that exist homogeneously in each aggregate particle having diameter in the range of 100 to 200 nm for sufficient desired opacity and strength and adhesion in terms of washability and scrub resistance, adapted for anyone of high PVC emulsion paint with reduced inorganic pigment, binder for concrete coating, having the characteristics improved opacity and reduced strength, better coverage and ease of application in concrete coatings based on the involvement of said low molecular weight nonionic polysaccharide/sta rch.
According to another aspect a process for the synthesis of biopolymer based copolymer emulsion is provided comprising sequential seeded multi stage free- radical aqueous polymerization of monomers including styrene and butyl acrylate as essential monomers in the presence of non-degraded, non-gelatinized polysaccharide and obtaining therefrom biopolymer doped acrylic latex including copolymer of styrene and butyl acrylate onto non-degraded, non-gelatinized polysaccharide as a stable flowable polymer dispersion having solid content in the range of 30-50% by wt. free of any phase separation, viscosity increase and gelation upon storage.
Preferably said process comprises the steps of
Preparing aqueous polymer dispersion comprising monomers including styrene and butyl acrylate as essential monomers taken in the ratio range of styrene: butyl acrylate in the ratio range of above 50: 50 to below 70 :30, preferably 55:45, and polymerizing said monomers by free radical aqueous polymerization in the presence of non-degraded, non-gelatinized polysaccharide preferably tapioca dextrin at emulsion polymerization temperature of 65 to 95°C, preferably from 75 to 85°C. According to another preferred aspect of said process said monomer as 100 parts by weight monomer or mixed monomer comprises 0 to 70% by weight of vinyl aromatic monomer, 0 to 50 % by weight of an ethylenically unsaturated monomer together with unsaturated carboxylic acid selected from unsaturated monobasic acids such as methacrylic acid and acrylic acid preferably acrylic acid in an amount of 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of total monomers making up said copolymer, which said monomers are polymerized in a sequential seeded multistage semi-continuous process in presence of 3 to 10 % by weight dextrins free of any derivatization, gelantization and thinning.
Preferably said process comprises the steps of
Charging entire amount of said dextrin as aqueous solution into the polymerization reactor followed by surface active agents/emulsifiers with intense and homogeneous mixing prior to addition of emulsified monomer mixture, with initial solid content kept at 15 to 20% by weight, for seeding;
Carrying out free-radical aqueous emulsion polymerization neither as a batch process or as feed process, preferably feed process in presence of polymerization initiators wherein part of the polymerization batch is heated to said polymerization temperature and partially polymerized, followed by feeding the remainder of the polymerization batch to the polymerization zone continuously, preferably via separate feed streams said separate feed streams enabling feeding said monomers frequently to the polymerization zone post pre-emulsification with surface active agents/emulsifiers to favour reduced surface tension and simplify stirring and comprises two stages:
Wherein in the first stage emulsified monomer mixture and catalyst are fed into the polymerization reactor over a period of 45 to 75 minutes while maintaining the polymerization temperature.
Wherein in the second stage polymerization is carried out by adding additional emulsified monomers and catalyst mixture to the dextrin polymer dispersion in the polymerization reactor for about 150 to 180 minutes. Preferably is said process said polymerization initiators include persulfates of potassium persulfate, sodium persulfate and ammonium persulfate; organic peroxides such benzoyl hydroperoxide, redox initiators by combining them with a reducing agent such as sodium formaldehyde sulphoxalate; and wherein said surface active agent is includes anionic surface active agent, a nonionic surface active agent or a combination thereof includinganionic surface active agent comprising sodium alkylsulfate, sodium dialkylsulfosuccinate, nonionic surface active agents including polyoxyethylene alkyl ether and polyoxyethylenealkylphenol ether in amounts of 0.5 to 5 parts by weight per 100 parts by weight of all monomers.
More preferably said process providing for biopolymer doped acrylic latex comprises fine particle aggregates of biopolymer doped acrylic latex onto polysaccharides obtained of a mixture including styrene, butyl acrylate, unsaturated carboxylic acid and said biopolymer wherein said biopolymer exist homogeneously in each aggregate particle having diameter in the range of 100 to 200 nm for sufficient desired opacity and strength and adhesion in terms of washability and scrub resistance.
BRIEF DESCRIPTION OF FIGURES
Fig. 1 : illustrates at lower magnification (a) Standard batch (Cryo SEM); (b) dextrin post blended in latex (Cryo SEM);
Fig. 2: illustrates at higher magnification (a) Standard batch (Cryo SEM); (b) dextrin post blended in latex (Cryo SEM).
DETAILED DESCRIPTION OF THE INVENTION
As discussed hereinbefore, the present invention provides for a biopolymer based copolymer emulsion comprising biopolymer doped acrylic latex including copolymer of monomers including styrene and butyl acrylate on to non-degraded, non-gelatinized polysaccharide starch including starch/dextrin at low dosage together with the synthetic monomers in select amounts, thus providing for biopolymer based copolymer, preferably biopolymer doped acrylic latex and emulsions thereof suitable for concrete coating compositions. The starch/dextrin was locally bought as a packaged product and employed advantageously without any degradation or gelatinization or derivatization or thinning. The emulsion is especially useful for a high PVC (pigment volume concentration) emulsion paint. For a coating composition, presence of biopolymers at 3% to 10% in acrylic polymer was made using sequential polymerization process.
Said biopolymer based copolymer emulsion of the present invention comprising copolymer of monomers including styrene and butyl acrylate onto non-degraded, non-gelatinized polysaccharide was found to be surprisingly stable as a flowable polymer dispersion having solid content in the range as high as 30-50% by wt. free of any phase separation, viscosity increase and gelation upon storage. Solid content beyond this range could not be stabilized and below this range would not be suitable for concrete coating compositions.
According to an aspect of the present invention there is provided said biopolymer based copolymer dispersions preferably biopolymer doped acrylic latex and dispersions thereof comprising monomers, surfactants, initiator and non- polymerizablecrosslinkers adapted as a binder for concrete coating, said copolymer dispersion being surfactant stabilized.
Starch/dextrin based thermoplastic polymer of the present invention is made using free radical emulsion polymerization to find application in water based decorative paint for concrete surface.
According to another aspect in the process of the present invention is based on sequential free-radical polymerization wherein synthetic monomers belonging to the class of water insoluble hydrophobic monomer including styrene is used free of any VAM monomer, having no affinity for dextrin, and wherein styrene acrylic copolymer emulsion synthesized in presence of dextrin in the monomer mixture results in intimately dextrin modified latex with substantially reduced water leachability of dextrin.
According to yet another aspect of the present invention there is provided a copolymer composition made using sequential polymerization that greatly enhance the compatibility among the components (starch and polymers) and in turn forms a network structure by combining polymers. The resulting low molecular weight nonionic starch /Dextrin preferably Tapioca starch based styrene acrylic thermoplastic polymer employed to make high PVC emulsion paint of the present invention display improved opacity and reducing strength, better coverage and ease of application in concrete.
EXAMPLES:
Preparation of biopolymer based copolymer dispersion
According to an embodiment of the present invention the aqueous polymer dispersion according to the present invention is preferably prepared by polymerizing the monomers by the free radical aqueous polymerization process in the presence of tapioca dextrin. The emulsion polymerization temperature is generally from 65 to 95°C, preferably from 75 to 85°C. The polymerization medium is water.
In accordance with the present process 100 parts by weight monomer or mixed monomer consisting of 0 to 70% by weight of vinyl aromatic monomer, 0 to 50 % by weight of an ethylenically unsaturated monomer are polymerized in a multistage semicontinuous process in presence of 0 to 10 % by weight dextrins, and in which the content of dextrin having low molecular weight preferably Tapioca starch being free of any derivatization, gelantisation and thinning. In a preferred process of this invention the entire amount of the aqueous dextrin solution is charged into the polymerization reactor followed by surface active agents. The whole composition is intensely and homogeneously mixed before the addition of monomer mixture.
The emulsion polymerization can be carried out either as a batch process or in the form of a feed process. Preference is given to the feed process, in which part of the polymerization batch is heated to the polymerization temperature and partially polymerized, and the remainder of the polymerization batch is subsequently fed to the polymerization zone continuously, usually via a separate feed streams, while maintaining the polymerizationtemperature. In an application wise advantageous manner, the initially introduced emulsified monomer mixture contains small amounts of emulsifiers, in order to reduce the surface tension of the dispersion medium and thus to simplify stirring in. The monomers are therefore frequently fed to the polymerization zone after pre-emulsification with these assistant emulsifiers.
Preparation of a dextrin polymer dispersion in accordance with the invention may be accomplished by charging water, tapioca dextrin and surfactant into a reaction vessel. The initial solid content is preferably from about 15 to 20% by weight. After seeding, polymerization is accomplished by a dual feed process wherein emulsified monomer mixture and catalyst are fed in the reaction vessel over a period Of 45 to 75 minutes. Additionally, a second stage of polymerization is carried out by adding additional emulsified monomers and catalyst to the dextrin polymer dispersion to about 150 to 180 minutes.
The unsaturated carboxylic acid used in the present invention is selected from unsaturated monobasic acids such as methacrylic acid and acrylic acid. Acrylic acids are preferred. The unsaturated carboxylic acid is used in an amount of 0.5 to 5 parts by weight, more preferably 1 to 3 parts by weight, per 100 parts by weight of total monomers used in making copolymer. If the amount is less than 0.5 parts by weight the kettle hygiene and coagulum formulation is very high. If the amount is greater than 5 parts by weight the resulting polymer particle will be poor in water resistance and alkali resistance.
The surface active agent is used in the present invention can be an anionic surface active agent, a nonionic surface active agent or a combination thereof. Useful anionic surface active agents include, for example, sodium alkylsulfate and sodium dialkylsulfosuccinate. Useful nonionic surface active agents include, for example, polyoxyethylene alkyl ether and polyoxyethyleneaikylphenol ether. The amount of surface active agent used is critical in stabilizing polymer particle in aqueous medium. It is usually used in an amount of about 0.5 to 5 parts by weight per 100 parts by weight of all monomers.
As a polymerization initiator, there can be used any of various polymerization initiators that are commonly used in emulsion polymerization. Useful polymerization initiators include, for example, persulfates such as potassium persulfate, sodium persulfate and ammonium persulfate; organic peroxides such benzoyl hydroperoxide. If desired, they can also be used as redox initiators by combining them with a reducing agent such as sodium formaldehyde sulphoxalate.
The polymer thus obtained comprises fine particle aggregates formed from a mixture of a copolymer of styrene and butyl acrylate composed of an unsaturated carboxylic acid and a biopolymer exist homogeneously in each aggregate particle, the aggregate particles formed from polymer component have a diameter of 100 to 200 nm. If the diameter of the particles formed is smaller than 100 nm, the resulting emulsion will fail to provide sufficient desired opacity and reducing strength, while if it is larger than 200 nm, the resulting emulsion will be poor in opacity, reducing strength and adhesion in terms of washability and scrub resistance. The particle diameter ca n be controlled by varying the amount of first and second stage copolymer composition, the amount of surface active agent used in the reactor cha rge a nd the amount of initiator used for polymerization . Thus in accordance with the object of the present invention a process could be achieved for the production of dextrin polymer dispersion which ca n be ca rried out in a simple manner and which results in stable, flowable, aq ueous polymer dispersion having low viscosity and a solid content of at least 30% by weight an d most preferably above 40% by weig ht.
The dextrin polymer dispersion composition thus described does not have the problems of phase sepa ration, undue increase in viscosity upon storage and gelation . The difficulty of having high solid content together with polysaccha ride incorporation in the levels of 3% to 10% and yet reaching to stabilized biopolymer based copolymer emulsion without any problems of phase sepa ration, undue increase in viscosity upon storage and gelation, cou ld be only achieved not only because of select monomers styrene-butyl acrylate combination employed in select ratios provid ing for the desired MFFT but also because of the select process employed .
It was thus su rprisingly found by way of the present invention that a surfactant stabilized styrene acrylic polymer emulsion involving sta rch in select a mounts, free of any derivatization, gelantisation and thinning, could be employed as asecondary binding agent that allows styrene and butyl acrylate being two hydrophobic monomers to polymerize without any difficulty in the presence of a macromolecule like sta rch .
Characterization of biopolymer based copolymer dispersion
Such a styrene acrylic copolymer emulsion synthesized in presence of starch/dextrin, prefera bly low molecular weig ht non-ionic sta rch (dextrin) preferably Tapioca starch free from any degradation, derivatization, gelantisation and thinning, in the monomer mixture, results in intimately dextrin modified latex that substantially reduces water leachability of dextrin as demonstrated by difference in MFFT, washability and scrub resistance of high PVC paint prepared out of this latex. This differentiation is as against a dextrin post blended styrene acrylic latex or paint of equivalent composition Fig. la, lb.
At same magnification, the standard batch shows presence foreign (dextrin) particles as filler in between polymer matrix. But in post blended latex, no such filler was visible. Also the alkali resistance of post blended latex is poor as compared to standard batch when dextrin was used during reaction.
Said biopolymer doped acrylic latex of the present invention comprises fine particle aggregates including said copolymer of styrene, butyl acrylate including unsaturated carboxylic acid, onto polysaccharides, as biopolymer that exist homogeneously in each aggregate particle having diameter in the range of 100 to 200 nm for sufficient desired opacity and strength and adhesion in terms of washability and scrub resistance.
According to an aspect of the present invention there is provided a synthetic monomer ratio of 47: 53 (BA: STY) in the emulsion composition together with starch/dextrin in select amounts displaying optimum MFFT (minimum film formation temperature) of the polymer film. In isolation of these either the film becomes tacky or brittle.
The select monomer ratio helps in maintaining optimum hardness during film formation. The emulsion in being used for high PVC coating application, it is important to exhibit a balance between softness and hardness of the film. It was found that whenever the ratio is changed, the glass transition temperature (Tg) either increases or decreases. An increased Tg results in hard film and hence poor adhesion to substrate and also cracks in film. When Tg is decreased, a softer film is formed that leads to poor dirt repellency in exterior application.
It was thus significantly found by way of the present invention that monomers other than styrene and butyl acrylate such as other acrylates or methacrylates, are less compatible with the non-gelatinized, non-degraded starch, as the required properties could not be achieved. Styrene and butyl acrylates are the two most hydrophobic monomers that are difficult to polymerize in presence of oligomers like starch/dextrin in their non-degraded, non-derivatized, non- gelantinized and non-thinned form, yet which polymerization however, could be achieved based on select sequential free-radical polymerization based process by employing styrene and butyl acrylate monomers in select ratios together with other monomers. Other non-compatible monomers can be incorporated in the biopolymer based copolymer emulsion of the present invention to be able to incorporate non-gelatinized, non-degraded starch only when the desired styrene and butyl acrylate monomer ratio is met.
Apart from the above non-compatibility of other methacrylates, such non compatibility turns into an advantage and leads to biopolymer based copolymer of the present invention that is cost effective and economical for high PVC paint application.
The following are the advantages in relation to the present invention :
1. The dextrin-based copolymer composition is responsible for improved opacity and reducing strength, better coverage and ease of application in concrete coatings.
2. Low molecular weight nonionic starch (Dextrin) Tapioca starch without derivatization, gelantisation and thinning could be employed to make the copolymer emulsion. 3. Use of inexpensive polymers which is not only renewable but also biodegradable as a replacement to synthetic monomers and 'mineral earths' material including expensive white inorganic pigments. The copolymer emulsion comprising biopolymer doped acrylic latex finds commercial end use and application in high PVC decorative paints to be a cost- effective alternative to pure styrene acrylic backbone, gives boost to a greener product and also provides a scope to reduce petroleum-based monomer content in polymer emulsion and possible reduction in inorganic pigment.