CS266975B1 - Method of tough polyvinyl chloride production - Google Patents

Abstract

Tough polyvinyl chloride is produced by suspension homopolymerization and / or copolymerization - by vaccinating vinyl chloride on A specially prepared elastomer that is on base of a homopolymer or copolymer of alkyl acrylates. Suspension polymerization and / or copolymerization (vaccination) is performed after the presence of a reaction-time modifier and the grain size of the tough suspension "polyvinyl chloride" is at least one calcium or a magnesium carboxylic acid salt C 1 to C 8 including 5-hydroxyvaleric acid and 6-hydroxycaproic acid. modifier is applied in an amount of 0.005 to 0.5% by weight. (0.01 to 0.2 wt.%), Calculated on vinyl chloride. The method is suitable for the production of tough PVC in the chemical industry; reaches in compared to the prior art autoclave performance, even flow responses, lower power consumption, narrower grain grain distribution, minimal called. excess and higher bulk density.

Description

The invention relates to a process for the production of a suspension of tough polyvinyl chloride of the desired bulk density by suspension copolymerization, resp. by grafting with a special chloride of a special elastomer or by suspension polymerization of vinyl chloride in the presence of said elastomer and defined amounts of a modifier of the course of the reaction and grain distribution of the produced polyvinyl chloride high-strength powder produced.

It is generally accepted that in addition to the many obvious advantages of the various types of polyvinyl chloride (PVC), their disadvantage is their relatively low toughness, which limits their use. Therefore, it is usually modified to improve the toughness of PVC, both by mechanically mixing different elastomers into the PVC mixture during their processing, and by different ways of incorporating the elastomer into the PVC before processing. This can be done by seeding a suitable elastomer on a PVC matrix or by seeding with vinyl chloride, or by copolymerizing vinyl chloride to a suitable elastomer.

In the first case, a suitable monomer, e.g. alkyl acrylate is added to the PVC emulsion or suspension, or the dry PVC powder is allowed to swell with monomer, and only then is the suspension or emulsion prepared to react with the swelling monomer (U.S. Pat. No. 3,544,661; GDR Pat. No. 143,081 and U.S. Pat. 149 074).

In the second case, vinyl chloride is grafted onto elastic rubbery polymers or copolymers, where the elastic backbone imparts the desired properties to the resulting material (NSR pat. 1,082,734, 1,090,866 and 1,090,857). Depending on the type of elastomer used in the grafting, the copolymer thus prepared has different properties. The basic elastomer affects not only the toughness of the material, but also its processing and performance properties. However, the rubbery phase must ensure an increase in toughness in a sufficient temperature range. This means that the elastomeric component must have a glassy transition substantially below the temperature of use of the mixture. Thus, these processes more or less make it possible to produce tough polyvinyl chloride (hPVC), but with relatively low values of toughness or impact resistance, indicated, inter alia, by notched flexural and tensile impact strengths determined by standard procedures or insufficient reproducibility of properties. These toughness parameters are also highly dependent on the temperature fluctuations to which the product is exposed during use.

Balej (USSR Pat. No. 513,048; NSR Pat. No. 1,227,656 and 2,231,600; U.S. Pat. No. 3,966,846 and U.S. Pat. polyalkyl acrylates or copolymers of alkyl acrylates with at least one other comonomer, such as styrene, acrylonitrile, vinyl acetate, methyl methacrylate, itaconic acid, maleic acid, 1,3-butadiene, isoprene, chloroprene, vinylidene chloride, ethylene and propylene (V. Brit. ). This is usually a two-stage process in which, in the first stage, an elastomer is prepared mainly by emulsion polymerization and in the second stage it is prepared in an emulsion or suspension! inoculates vinyl chloride. However, the processes do not ensure high efficiency and good reproducibility of properties, especially when applying hPVC products at larger temperature fluctuations. The addition of coagulants based on polyvalent metal cations or quaternary ammonium compounds, such as calcium chloride, magnesium chloride, ferric chloride, aluminum chlorite, aluminum sulphate and calcium sulphate (U.S. Pat. Nos. 3,669,914 and 3,661,867; British Pat. 1,460,139). Also, the obtained hPVC does not have satisfactory technical properties and the course of polymerization, resp. copolymerization is difficult to control, there is considerable gel-effect with all the consequences for the conduct of the reaction and the useful properties of the produced powder. '

Significant technical progress is the method of production of hPVC according to Czechoslovakia. of the author's certificate 257 356, which uses both a specially prepared elastomer and a modification of the homopolymerization and / or copolymerization process. Nevertheless, the process requires intensive mixing of the polymerization or copolymerization mixture, less filling and all the lower productivity of autoclaves. During production, an increase in the viscosity of the reaction medium has a negative effect, and a higher concentration of dispersants is required during normal autoclave filling. However, all the advantages of the above-mentioned hPVC production process take advantage of and, moreover, solve the remaining technical problems of the production method according to the invention.

CS 266 975 Bl

Process for the production of tough polyvinyl chloride by suspension polymerization and / or copolymerization of vinyl chloride in the presence of an aqueous dispersion of elastomer based on homopolymer and / or copolymer of alkyl acrylate with vinyl monomer or monomers, in an amount of 3 to 35% by weight of elastomer. or initiators and in the presence of a protective colloid or colloids and auxiliaries, at a temperature of 10 to 90 ° C, until a vinyl chloride conversion of 70 to 100% is achieved, the reaction progress modifier and the grain size of the tough polyvinyl chloride suspension is at least one calcium and / or magnesium carboxylic acid salt C 1 to C 8, preferably calcium and / or magnesium formate, in an amount of 0.005 to 0.5% by weight, preferably 0.01 to 0.2% by weight. % by weight of calcium and / or magnesium to vinyl chloride.

The advantage of the production method according to the invention is the higher productivity of autoclaves enabled by their higher filling, uniform course of copolymerization, resp. inoculation, practically with the exclusion of the gel effect, a narrower distribution of the powdered tough polyvinyl chloride and only a minimal proportion of coarse grains. Last but not least, the method makes it possible to reduce the concentration and thus the consumption of dispersants, to reduce the effect of emulsifiers and also in comparison with the addition of calcium chloride, not only to substantially reduce the level of chloride ions in mother liquors, but to obtain a more compact hPVC powder and higher bulk density.

The production of a tough polyvinyl chloride according to the invention is more precisely defined, in particular the production of a tough, vinyl chloride grafted (split) elastomer, the elastomer being a homopolymer of alkyl acrylates or a copolymer of alkyl acrylates with other comonomers such as methyl methacrylate, 1,3-butyrene VC etc. The production method for said purposes of a high-quality elastomer is known, e.g. from MS. author's certificate 257 150. Thus, it is the production of a tough copolymer material.

Suitable auxiliaries for the process according to the invention are antioxidants or reducing agents, molecular weight regulators, transporters, pH regulators, surfactants or ammonia additives.

The excipient, resp. polymerization course modifier, resp. seeding (cleavage), whether the copolymerization is at least one calcium and / or magnesium salt of a C 1 to C 8 carboxylic acid. It is understood that it can also be a mixture of calcium and magnesium salts of mixture of C _x to C, wherein the carboxylic acid C ₅ to C shall include the 5-hydroxyvaleric acid and 6-hydroxycaproic. From the point of view of technical availability and easy handling, as well as practically negligible toxicity for wastewater, dormant formate and magnesium formate are particularly suitable.

Lower than stated amounts of magnesium or calcium salts in the reaction medium, expressed as the amount of calcium or magnesium by weight of vinyl chloride, are no longer effective in modifying the production process according to the invention and higher than 0.5% by weight again cause coarsening of the product grain.

Further data on the implementation of the method according to the invention, in addition to the already mentioned MS. copyright certificates, as well as other benefits, are apparent mainly from the examples.

Example 1

Preparation of elastomer

135 kg of demineralized water and 2,400 g of an aqueous solution of sodium alkanesulfonate, known under the trade name Emulsifier E30 (with an average number of carbon atoms in the molecule of 15; sodium content; sodium content; salts of alkanesulfonic acids with respect to 100% of dry matter is 80 to 85% by weight, sodium chloride content 0.2 to 2% by weight, neutral oils 0.05 to 1% by weight) with a concentration of 20% by weight, (also known as Mersolate ).

CS 266 975 Bl

8 kg of 2-ethylhexyl acrylate are added with stirring and the reaction mixture is heated to 35 [deg.] C. under a nitrogen atmosphere. The reaction medium was added to 205 g of a potassium persulfate Joint K_S _{of about} 0, 100 cm of saturated aqueous sodium chloride, cuprous copper C, and 144 g of sodium peroxodisulfate 22 xxo the _N S _N O '. 2H „0. After 10 min. from the start of the reaction, which is manifested by the evolution of XXOX heat of reaction, a further 8 kg of 2-ethylhexyl acrylate are added to the reaction medium at once and for 15 min.

after the start of the reaction, t. j. 5 min. after the addition of a second portion of 2-ethylhexyl acrylate, 3 kg of vinyl chloride are added to the reaction medium, the temperature of the reaction mixture being maintained at 35 + 0.1 [deg.] C. for a further 1.5 h. The contents of the autoclave are then heated to 80 DEG C. and kept for 1 hour, after which they are cooled to room temperature. The vapor space of the autoclave is then thoroughly freed of a few monomers. The elastomer copolymer dispersion thus obtained is also suitable as a grafted substrate for the production of a suspension of tough polyvinyl chloride.

Preparation of a suspension of tough polyvinyl chloride

7 dm of demineralized water are pumped into a 50 dm 2 stainless steel autoclave equipped with a stirrer, a β-3 duplicator and accessories. Then 875 cm 3 of an aqueous solution of methylhydroxypropylcellulose (Methocel 50 F), 6 kg of a copolymer dispersion of poly- (2-ethylhexyl acrylate) - inoculated with vinyl chloride, 200 g of a mixed initiator (EHP-80), consisting of a mixture of peroxides, are added.

ΓCH ₀ (CH ₀ ) n CHCl.H.JCH.OCO-OO-COC.H2; CHCO-OO-COC, Η .; * -3x3 zb χ obob ob

CH ₃ (CH ₂ ) ₃ CH (C ₂ H ₅ ) CH ₂ OCO-OO-OCOCH ₂ -CH (C ₂ H ₅ ) (CH ₂ ) ₃ -CH ₃ 7 'at a concentration of 50% by weight, in xylene as solvent . The autoclave is then closed, the air is removed and 7 kg of vinyl chloride are added. After the addition of vinyl chloride, the reaction mixture was stirred for 20 min. homogenized, then heated to 56 ° C and maintained at this temperature until the pressure in the autoclave drops by 0.4 MPa. During the polymerization, resp. copolymerization is a demanding removal of heat of reaction; the end of the reaction is characterized by a gel effect. The agitator load during the polymerization, resp. vaccination is increasing.

Unreacted vinyl chloride and other gaseous components are then released from the autoclave. The contents of the autoclave are then cooled and drained. After completion of the suspension graft copolymerization, the mother liquors have a pH = 2.6 and a chloride ion content (Cl <H in the final mother liquor, 134 mg / dm after opening the autoclave. The product is viscous to slurry. The crude product is then centrifuged, washed with distilled or at least demineralized water and dried at 60 ° C to constant weight.

The dried product has a bulk density of 484 g / dm with a copolymerized 2-ethylhexyl acrylate content of 8.5% by weight.

The sieve analysis of the product is based on the following: 76.4% of the product remains on the 0.250 mm sieve; on sieve 0.200 mm 6.4%; on 0.180 mm 0.2% nets; on a sieve of 0.10 mm 1.2% and 0.063 mm 0.2% by weight; the overflow is 15.8% by weight.

Notched toughness is 82 kJ / m ² and Vicata softening temperature 84.7 ° C. The test specimens in this and other examples are prepared according to a uniform procedure by extruding mixtures having the composition:

100 masses, parts of tough PVC,

1.9 parts by weight of dibutyltin triglycol ester (Sn-31 stabilizer), 0.7 parts by weight of adipic acid dialkyl ester (Loxiol G-60);

1.2 wt. Parts, calcium stearate;

0.3 parts by weight of stearic acid;

1.8 wt, parts of processing modifier (Paraloid K-120 N);

CS 266 975 Bl

1.0 parts by weight of titanium dioxide (Pretiox RD-53);

3.0 parts by weight of floating chalk (Omnia BSH).

The extrusion mixture is prepared in a hot fluid mixer, the temperature in this processing phase reaching about 120 ° C. Next, the cooled mixture is processed by extrusion or calendering.

Example 2

The polymerization autoclave and the initial procedure up to the closing of the autoclave and the dosing of 7 kg of monomeric vinyl chloride are similar to the process for the preparation of suspended polyvinyl chloride in Example 1. After dosing the vinyl chloride, the autoclave content is homogenized for 10 min. and then an aqueous solution containing 10 g of calcium chloride is added. Then pp another 10 min. homogenization, the contents of the autoclave are heated and polymerized or copolymerized as in Example 1. The course of the reaction is regular, the load of the stirrer increases only slightly, resp. similar to standard suspension homopolymers of vinyl chloride. After a pressure drop of 0.4 MPa, the contents of the autoclave are cooled, the unreacted vinyl chloride and the other gaseous components are removed and the contents of the autoclave are discharged. The product is a conventional suspension polymerization product of vinyl chloride. The mother liquor has a pH = 3.6 and a chloride ion content (Cl ') of 380 mg / dm. The product has a bulk density of 486 g / dm and the following granulometry:

sewn mesh size (mm) 0.25 0.20 0.18 0.10 0.063 overflow through the sewing amount of powder (% by weight) 23.0 20.4 5.6 19.2 6.4 25.4

After processing, the product has a notched toughness of 7.3% by weight, acrylate content 2

31.2 kJ / m.

Under otherwise similar conditions, instead of only 10 g of calcium chloride, 12 g of magnesium chloride are added to the copolymerization medium.

The obtained suspension tough polyvinyl chloride differs in part by a lower proportion of the so-called

excess share, t. j. powder particles over 0.25 mm, t. j. instead of 23.0% is 19.9% by weight.

In both cases, however, it is too high a proportion of coarse-grained powder, which is difficult to use on an industrial scale.

Example 3

The polymerization autoclave and the procedure are similar to Example 2, but the difference is that after the addition of vinyl chloride, 10 g of calcium formate are added to the homogenized reaction medium instead of 10 g of calcium chloride. The reaction proceeds evenly and the agitation of the stirrer is minimal. The mother liquors have, after the polymerization, resp. copolymerization -3 3 pH = 3.7 and chloride ion content 126 mg / dm. The product obtained has a bulk density of 546 g / dm and the following granulometry:

the size of the sewing (mm) 0.25 0.20 0.18 0.10 0.063 overflow through the sewing quantity powder (% by weight) 3.2 10.8 16.4 60.8 6.6 2.2

Content of incorporated 2-ethylhexyl acrylate in the suspension! 8.6% by weight, and the product prepared by the process of Example 1 has a notched toughness of 78.9 kJ / m 2.

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Under otherwise similar conditions, but using nu calcium, the so-called excess share, t. j. above 2 sample yield 78.7 kJ / m.

g of magnesium formate instead of 10 g of 2.5 mm formate constitutes only Q.9% by weight, and notched mass. 28.7% by weight) and magnesium n-valeranium (36.3% by weight) constitute an excess of 0.93% by weight, and the notched tensile strength of the sample is 77.9 kJ / m 2.

Example 4

10 kg of demineralized water are pumped into a 50 dm ³ autoclave, 2,000 g of a 2% strength by weight aqueous solution of methylhydroxypropylcellulose, 40 g of the mixed initiator (EHP-80) specified in Example 1 and 10 kg of poly-2-ethylhexyl acrylate are added. dispersion). The autoclave is closed, the vapor space of the autoclave is deaerated (inerted) and 16 kg of vinyl chloride are added. After 10 min. ' By homogenization, 30 g of calcium formate in aqueous solution are added to the reaction medium. After another 10 min. homogenization, the contents of the autoclave are heated to the polymerization or copolymerization temperature of 56 ° C and polymerized to a pressure drop of 0.4 MPa. The reaction proceeds regularly and the increase in the load on the stirrer during the polymerization is minimal. After completion of the polymerization, the mother liquor has a pH of 4.2 and a content of chloride (-) 3 ions (Cl) of 84 mg / dm 2. The product obtained has the following particle size distribution:

sewn mesh size (mm) 0.25 0.20 0.18 0.10 0.063 overflow through the sewing amount of powder (% by weight) 4.8 8.6 5.8 42.2 28.4 10.2

The bodies prepared by extrusion according to the weight of the copolymerized 2-ethylhexyl acrylate in Example 1 have a notched toughness of 41 kJ / m at a content of 6.6% 2.

Example 5 3 68 dm of demineralized water, 6.25 kg of a 2% by weight aqueous solution of methylhydroxypropylcellulose, 50 g of a mixed initiator (50 g of mixed initiator) are metered into a 250. EHP-80) characterized in Example 1 and 35 kg of a copolymeric poly (2-ethylhexyl) acrylate-vinyl chloride dispersion specified in Part 1 of Example 1. The autoclave is then closed and air is removed and 50 kg of vinyl chloride are added. After 20 min. homogenization, the contents of the autoclave are heated to 56 ° C and the reaction mixture is maintained at this temperature until the pressure drops by 0.4 MPa. The contents of the autoclave are then cooled, degassed and the reaction mixture is drained. The mother liquor has a pH = 2.8 and a chloride ion content Cl 95 95 mg / dm ³ . The prepared suspension is filtered off, washed with demineralized water and dried in a leaf oven at 65 ° C. The regulation of the copolymerization temperature is difficult, at the end of the polymerization a significant gel effect is manifested. The prepared suspension is viscous, it has a considerable structural viscosity. After drying, it has a bulk density of 471 g / dm and the particle size distribution is as follows:

size

6k stitched (mm) 0.25 0.20 0.18 0.10 0.063 overflow through the sewing amount of powder (% by weight) 30.4 8.4 4.8 34.4 13.6 8.4

With an elastomeric component content of 7.9% by weight, the product obtained has a notched toughness of 56.3 kJ / m 2.

CS 266 975 Bl

Example 6

84 dm of demineralized water, 7.0 kg of a 2% strength by weight aqueous methylhydroxypropylcellulose solution, 55 g of the mixed initiator (EHP-80) specified in Example 1 and 45.0 dm of an aqueous copolymer dispersion are metered into the autoclave characterized in Example 5. of the elastomer, also specified in Example 1. After closing the autoclave and removing the air, 70 kg of vinyl chloride are added. After 10 min. By homogenizing the reaction mixture, 125 g of calcium formate in the form of a saturated aqueous solution are added to the autoclave. Heating of the reaction mixture to 56 ° C begins for 10 min. after the addition of calcium formate and at this temperature, the contents of the autoclave are maintained with stirring until the pressure drops by 0.4 MPa. The temperature control of the reaction medium is good, as it does not increase the stirrer load or the gel effect towards the ends of the copolymerization. After the pressure in the autoclave has dropped by 0.4 MPa, the contents of the autoclave are cooled, degassed and drained. The mother liquor has a pH of 4.2 and a Cl ion content of 77 mg / dm 2. The suspension is filtered off, washed with water and dried at 65 ° C. The product has a bulk density of 610 g / dm 2 and the following particle size distribution: size

Sk sewn (mm) 0.25 0.20 0.18 0.10 0.063 overflow through the sewing amount of powder (% by weight) 3.2 4.8 4.0 22.4 23.6 42.0

The processed product has a copolymerized 2-ethylhexyl acrylate content of 6.8% by weight, and the prepared bodies have a notched toughness of 54.4 kJ / m 2.

In another experiment carried out under otherwise similar conditions, only in addition to 125 g of calcium formate, a further 55 g of calcium acetate and 70 g of magnesium propionate are added, the product obtained has a bulk density of 627 g / turf and excess grain, i. j. above 0.25 mm (i.e. gross fraction) is only 1.1% by weight.

Claims (1)

OBJECT OF THE INVENTION Process for the production of tough polyvinyl chloride by suspension polymerization and / or copolymerization of vinyl chloride in the presence of an aqueous dispersion of elastomer based on homopolymer and / or copolymer of alkyl acrylate with vinyl monomer or monomers, in an amount of 3 to 35% by weight of elastomer. or initiators and in the presence of a protective colloid or colloids and optionally excipients, at a temperature of 10 to 90 ° C, until a vinyl chloride conversion of 70 to 100% is achieved, characterized in that the suspension component of suspension homopolymerization and / or copolymerization of vinyl chloride during the reaction and the grain size of the toughening polyvinyl chloride suspension is at least one calcium and / or magnesium salt of a carboxylic acid up to C 1, preferably calcium formate and / or magnesium formate, in an amount of 0.005 to 0.5% by weight, preferably 0.01 to 0.2% by weight of calcium and / or magnesium to vinyl chloride.