RU2275383C1 - Polyvinyl chloride with enhanced chemical stability in organic solvents and its using - Google Patents

Abstract

FIELD: chemistry of high-molecular polymers.

SUBSTANCE: invention relates to polyvinyl chloride and its using. Proposed suspension polyvinyl chloride has Fickentcher's constant value K_f = 77-88, and it represents powder consisting of porous unclear particles characterizing the specific surface value 1.0-4.0 m²/g and the porosity value 0.27-0.42, and enhanced chemical stability in organic solvents also. Polyvinyl chloride is prepared by an aqueous-suspension polymerization of the reaction mixture comprising vinyl chloride, stabilizing agent and peroxide initiating agent at average polymerization temperature 35-42° and revolution rate of mixer 0.5-3.5 s^-1. Polyvinyl chloride with abovementioned indices is used for making different plasticized materials with improved physical-mechanical indices.

EFFECT: improved and valuable properties of polymer.

3 cl, 2 tbl

Description

The present invention relates to the field of production of high molecular weight chemical compounds, in particular to suspension polyvinyl chloride (PVC), which is widely used in the production of two types of materials - non-plasticized (vinyl plastic, pipes, building and window profiles) and plasticized (cable and shoe plastic compounds, film materials, linoleum).

In terms of distribution in the technology, PVCS is the second largest in the world.

PVCs are obtained in an apparatus with a stirrer and a heat transfer jacket in an aqueous medium in the form of a suspension with an average particle size of 75-150 microns.

The quality of PVCs is determined by several indicators that are important both in the preparation of the polymer and in its processing.

The main indicators are:

- "Fikentcher’s constant", Kf, characterizes the average molecular weight of PVCA, the physico-mechanical properties of the polymer and finished products,

- "plasticizer absorption mass", characterizes the ability of PVC to absorb plasticizer when it is processed into plasticized products.

- "bulk density", determines the fill factor of the screw of the extrusion machines and their productivity.

- "particle size distribution", determines the particle size of the PVC, the ease of separation of the polymer from the suspension and drying, as well as the flowability of the polymer.

- specific surface - characterizes the coalescence of microglobul in the grain and the strength of the particles of PVC.

Currently, in industry, in the production of rigid and plasticized products, mainly several brands of PVCs are used with a range of Kf = 60-77 [Encyclopedia of Polymers, ed. V.A. Kargina, T.1, M .: Soviet Encyclopedia, 1972, p. 444]. Commercially available PVCs are characterized by a porosity of 0.20-0.26 or 20-26%, a specific surface area of ~ 0.5-1.0 m ² / g, are heterogeneous, can contain both porous (opaque) and non-porous (glassy) particles. The heterogeneity of the polymer is especially affected when it is processed into plasticized products, since porous and non-porous particles of the polymer absorb the plasticizer at different speeds, which leads to various defects during extrusion processing and the production of various films.

There are a large number of patents for the production of PVCs used in industry, as well as prescription techniques for producing highly porous polymers. For example, in US patent No. 5155189, C 08 F 2/20, publ. 10/13/92 describes PVCA with Kf = 69, porosity of 0.342 cm ³ / g and plasticizer absorption time of 297 s, obtained by polymerization in the presence of dispersants (first and second); the second dispersant is a derivative of esters of acrylic and / or methacrylic acids and contains terminal functional groups (carboxyl, hydroxyl, anhydride, alkyd, amine, isocyanate); the first dispersant is hydrolyzed polyvinyl alcohol, gelatin, cellulose, cellulose ether).

In another patent [US Patent No. 5342906, C 08 F 2/20, publ. 08/30/94] receive PVCA with KF = 67, bulk density 0.56 g / cm ³ , porosity of 24.5% by suspension polymerization of vinyl chloride in an aqueous medium, in the presence of a dispersing agent (polyvinyl alcohol) and an initiator soluble in the monomer; with vigorous stirring and heating

Patents are known in which PVCA is used with a high Fikentcher constant Kf.

So PVC with a Fikentcher constant of 80-110 with a bulk density of 0.2-0.35 g / cm ³ [RF patent No. 2085563, C 08 L 27/06, publ. 07.27.97] is used in polymer compositions from PVC as a modifier to improve the physical and mechanical properties of products. The disadvantage of this PVCA is the low bulk density and, accordingly, poor flowability, which makes it suitable only as a modifier.

In the patent of the Russian Federation No. 2249020, C 08 L 27/06, publ. 03/27/05, the authors use PVCA with Kf = 80-110 and a bulk density of 0.20-0.55 g / cm ³ in the polymer composition to obtain a miplastic separator. PVCA is used as an additive to emulsion PVC in an amount of 5-15 wt.% In order to increase the volumetric porosity of the separator, reduce electrical resistance while maintaining tensile strength and increase the productivity of the tape sintering machine. PVCA with KF = 80 ÷ 110 is obtained by suspension polymerization of VC in a reactor with a volume of V = 17 m ³ . 8700 kg of demineralized water, a dispersion stabilizer (methylhydroxypropyl cellulose or polyvinyl alcohol), the initiator is dicetyl peroxydicarbonate, an alkaline agent (sodium hydroxide or sodium bicarbonate) are charged into the reactor with an impeller mixer and a heat transfer jacket, 0.025 ÷ 0.06 wt.% To water and 5400 kg vinyl chloride. The coolant (water) is supplied to the reactor jacket. The process is carried out at a temperature of 32 ÷ 43 ° C for 6-12 hours. Unreacted vinyl chloride is removed from the reactor, the polymer is filtered and dried. Get a finely dispersed polymer KF = 80 ÷ 110 and a bulk density of 0.20 ÷ 0.55 g / cm ³ , determined according to GOST 11035.1-93.

The disadvantages of PVCs with KF = 80-110 and bulk density of 0.20-0.55 g / cm ³ include:

1. The bulk density of the PVCS powder is largely determined by the size, shape of the particles and does not fully characterize the internal structure of the PVC particles. In the indicated range of 0.2-0.55 g / cm ² , the presence of both porous and non-porous PVCA particles is possible, which, as shown above, affects the processing of PVCA into products.

2. To obtain PVCA with a Kf constant of more than 89, special expensive low-temperature polymerization initiators are required that are not currently used in industrial production. The use of known initiators (peroxides or asymmetric perfers) used in the production of serial PVCs leads to a delay in the polymerization process. The use of highly active initiators such as acetylcyclohexylsulfanyl peroxide (ACSP) leads to increased crust formation on the walls of the reactor, which makes obtaining PVCA with a Kf constant of more than 89 economically unprofitable.

When producing PVCA with Kf = 77-88 at an average polymerization temperature of 35-42 ° C, peroxide initiators such as peroxides can be used: 1,1,3,3tetramethylbutylperoxyneodecanoate, tertamylperoxyneodecanoate, didvaethylhexylperoxydicarbonate, dicetyl peroxydicarbonates or other peroxydicarbonates, and currently in industry.

3. When processing compositions based on PVCA with Kf = 89-110, higher temperatures are required than when processing serial PVCA, which is very difficult on existing equipment.

The closest in technical essence is PVCA with KF = 74, a well-absorbing plasticizer, due to the high porosity [US Patent No. 5286796, C 08 F, publ. 02/15/94], and the producing polymer without fish eyes (glassy particles) is obtained by water-suspension polymerization of vinyl chloride using (a) polyvinyl acetate with a saponification degree of 75 to 99% and an average degree of polymerization of 1500-2700 and (or) ( b) hydroxypropyl methylcellulose with a degree of substitution of methyl groups of 26-30% and hydroxypropyl groups of 4-15% with a viscosity of 2% aqueous solution at 20 ° C in the range from 5 to 4000 cP, and also (c) from 0.002 to 0, 2 hours (per 100 parts by weight of vinyl chloride) of water-insoluble polyvinyl acetate with a degree of saponification of 20-60% and a degree of polymerization from 2000-30000. The polymerization is carried out at a temperature of 51 ° C and stirring, and complete when the pressure in the reactor drops to 5.0 ati. The residual vinyl chloride is then blown off, the polymer is dried and dried. PVCA is obtained with constant Kf = 74, bulk density 0.51 g / cm ³ , plasticizer absorption mass 34.3%, and a small amount of fish eyes in the polymer.

Series PVCA is practically resistant to water, salt solutions, most acids, alkaline solutions, mineral oils and some organic solvents, but not resistant to ketones, aromatic hydrocarbons, esters [Kryzhanovsky VK, Kerber ML, Burlov V .V., Patimatchenko A.D. Production of products from polymeric materials. - St. Petersburg: Profession, 2004. p.99, 100].

According to GOST 12020-72, the resistance of a polymer material to aggressive media is evaluated by the change in its mass: the greater the change in mass, the lower the resistance of this material [Kryzhanovsky V.K., Kerber M.L., Burlov V.V., Patimatchenko A.D. . Production of products from polymeric materials. - St. Petersburg: Profession, 2004. p.98].

For example, when exposed to a PVCA powder with Kf = 58 and 74, solvent R-4 (12 wt.% Butyl acetate, 26 wt.% Acetone, 62 wt.% Toluene) [GOST 7827-74, Solvents of grades R-4, R- 4A, R-5, R-5A, R-12, R-24 for paints and varnishes. - M .: Publishing house of standards, 1987] at a temperature of 50 ° C for 1 hour, there was a complete destruction of the polymer particles with its subsequent complete dissolution.

An object of the invention is to increase the chemical resistance of PVCs and to obtain material based on it with improved physical and mechanical characteristics.

The task is achieved by suspension PVCV polyvinyl chloride with a Fikentcher constant K _Ф = 77-88, which is a powder consisting of porous opaque particles, characterized by a specific surface area of 1.0-4.0 m ² / g and a porosity value of 0.27-0, 42, obtained by water-suspension polymerization of a reaction mixture containing vinyl chloride, an emulsion stabilizer, a peroxide initiator, at an average polymerization temperature of 35-42 ° C and a stirrer rotation speed of 0.5-3.5 s ^-1 .

As a stabilizer in the suspension polymerization of vinyl chloride to obtain polyvinyl chloride with the indicated characteristics, for example, polyvinyl alcohols, cellulose ethers and others traditionally used in the preparation of polyvinyl chloride are used.

The process of suspension polymerization of vinyl chloride to obtain polyvinyl chloride with the indicated characteristics can also be carried out in the presence of various target additives, for example, in the presence of pH regulators, antioxidants, etc.

In the range we offer, the value of Kf = 77-88 when exposed to solvent P-4 at a temperature of 50 ° C for an hour, no destruction of the PVCA particles is observed, only their swelling occurs, which indicates its increased chemical resistance. In its pure form, the increased chemical resistance of PVCA particles is important when using PVCA as an adsorbent for trapping various organic substances [VM Ulyanov Gutkovich A.D. Shebyrev V.V. Technological equipment for the production of suspension polyvinyl chloride. Nizhny Novgorod, 2004 p.206], [Application No. 2004118117/15 (019680) dated 16.06.2004. The method of extraction of volatile chemical compounds from gas-air mixtures].

It is known that porosity determines the ability of a polymer to absorb a plasticizer and is related to the indicator “plasticizer absorption mass” by the dependence [Ulyanov VM, Rybkin EP, Gutkovich AD, Pishin G.A. Polyvinyl chloride. - M .: Chemistry, 1992, p.53]

ε _p = α _p / (70 + α _p ),

where ε _p - porosity of PVC,

α _p - plasticizer absorption mass, g / 100 g PVC.

However, a single porosity value is not enough to characterize the internal structure of the PVCA particles, since porosity characterizes only the void volume in the polymer particle. Another important characteristic of the porous structure of PVCA particles is the specific surface area. When processed into plasticized products, the developed specific surface allows the plasticizer to be quickly and evenly absorbed. The specific surface area of the polymer was determined by thermal desorption [Keltsev N.V. Fundamentals of adsorption technology, 2nd ed., Revised. and add. - M .: Chemistry, 1984, p.47].

When the porosity is less than 0.27 and the specific surface is less than 1.0 m ² / g, the polymer is morphologically heterogeneous, does not absorb plasticizer fast enough, which leads to defects during processing into plasticized products.

With a porosity of more than 0.42 and a specific surface area of more than 4.0 m ² / g, the polymer has a low bulk density, poor flowability and becomes non-technological. In addition, with a very high porosity, difficulties arise in the uniform distribution of the plasticizer in the polymer, since part of the polymer can absorb all of the plasticizer introduced into the composition, while the remaining part of the polymer will remain without plasticizer.

PVCA, characterized by values of porosity of 0.27-0.42 and a specific surface area of 1.0-4.0 m ² / g, has high morphological homogeneity (the absence of glassy non-porous particles) and good flowability, which provides improved physicomechanical characteristics of PVC - materials.

The following is a specific example of the preparation of suspension polyvinyl chloride as claimed in the invention.

Example. 8700 kg of the aqueous phase and 5400 kg of vinyl chloride and 0.2 wt.% (To vinyl chloride) of dicetyl peroxydicarbonate are charged as a peroxide initiator into a 17 m ³ reactor with a stirrer and a heat transfer jacket.

The aqueous phase contains 0.05 wt.% (To water) polyvinyl alcohols as a dispersion stabilizer, 0.015 wt.% (To water) sodium hydrogen carbonate as a pH regulator and 0.01 wt.% (To water) 4-methyl 2 , 6-ditretic butylphenol as an antioxidant. A coolant (water) with a temperature of 80 ° C is fed into the jacket of the reactor and the contents of the reactor are heated to a polymerization temperature of 40 ° C.

The polymerization process is carried out at a polymerization temperature of 40 ° C, and end when the pressure in the reactor drops by 1.5 ati from the regime. The polymerization process takes 8 hours. The number of revolutions of the mixer during the entire polymerization process is n = 3 s ^-1 . Impeller stirrer, diameter of stirrer d = 0.9 m.

The resulting PVCA was analyzed according to GOST 14332-78. The specific surface area was measured by thermal desorption of argon using a sorbtometer. The porosity of the particles was determined from the values of the irreversibly absorbed plasticizer, which is measured according to GOST 25265-82.

"Fikentcher's constant", K = 81,

"Plasticizer absorption mass", MPP = 34 g / 100 g PVC,

"The residue after sifting on sieve No. 0063" - 91%,

The specific surface is 1.4 m ² / g,

Porosity - 0.327.

PVCA-based polymer compositions are used to produce plasticized products. Plasticized products are characterized by high elasticity over a wide temperature range, usually from -40 to + 80 ° C, good dielectric characteristics, high water, benz, and oil resistance. The compounding of plastic compounds, as a rule, consists of a polymer, a plasticizer (from 10-15 to 30-40, sometimes up to 80-100%), various stabilizers, lubricants, dyes and other special additives.

A comparison was made of the physicomechanical characteristics of PVC - materials based on PVCA with Kf = 63, 70 and 81, obtained according to the same recipe, under the same processing conditions. As PVC, the polymer composition contains PVCS of grades S-6359M, S-7059M according to GOST 14332-78 or PVCS With Kf = 81. As an ester plasticizer - phthalic acid esters - dioctyl phthalate (DOP) GOST 8728-27. As a metal-containing stabilizer, the composition contains tribasic lead sulfate (TOSS TU 6-09-4098-75) and calcium stearate (StSa), TU 6-09-4104-85, as a lubricant stearin (St) GOST 6484-64.

Table 1 shows an approximate composition of the polymer composition to obtain products.

Table 1. The composition of the polymer composition Composition components The composition, wt.h. The composition, wt.h. The composition, wt.h. PVCS, KF = 63 one hundred PVCS, Kf = 70 one hundred PVCS, KF = 81 one hundred (DOP) dioctyl phthalate 50-70 50-70 50-70 (TOSS) tribasic lead sulfate 3 3 3 (StSa) calcium stearate 1,5 1,5 1,5 (St) stearin 0.3 0.3 0.3

In a preheated to 60-70 ° C, the mixer load 100 wt.h. PVCA with Kf = 63.70 or 81; 50-70 parts by weight DOF; 3 parts by weight TOSS; 1.5 parts by weight StSa; 0.3 parts by weight St raise the temperature to 100-110 ° C, mix the composition at a stirrer speed of 950 rpm for 40 minutes. The resulting composition is granulated on a screw extruder at temperatures in zones I - 136 + 10 ° C; II - 145 + 10 ° C; III - 155 + 10 ° C; head - 165 + 10 ° C.

From the obtained plastic compound on laboratory rolls VDE - 320-160 / 160, at a working roll temperature of -165 + 10 ° C and a blank roll temperature of 155 + 10 ° C, a film 1 ± 0.1 mm thick is rolled. Then, from the obtained film, in a hydraulic press in accordance with GOST 12019-66, plates of PVC - a material with a thickness of 2 ± 0.1 mm are pressed.

Test samples are made in accordance with GOST 5960-72. The strength and elongation at break are determined according to GOST 11262, the hardness of the samples is determined according to GOST 24621-81, the volume resistivity of the PVC material is carried out according to GOST 6433.2-71, the fragility temperature is determined according to GOST 16783. The results of comparative tests of PVC material are presented in table 2.

Table 2. Comparative physical and mechanical characteristics of PVC materials Strength, kgf / cm ² Relative extension,% Fragility temperature, ° С Kf DOP content, parts by weight DOP content, parts by weight DOP content, parts by weight fifty 60 70 fifty 60 70 fifty 60 70 81 250 220 200 300 320 330 - 55 - 60 - 60 70 175 145 130 275 290 320 - 45 - 52 - 55 63 172 140 115 248 273 298 - 40 - 48 - fifty

Strength, elongation and brittle temperature, characterizing the frost resistance of the material, are the main indicators that determine the properties of PVC materials. As can be seen from the table, the values of these indicators are higher for PVCs with Kf = 81.

Thus, the above data indicate that suspension polyvinyl chloride with a Fikentcher constant Kf = 77-88 in the form of a powder consisting of porous particles with a specific surface area of 1.0-4.0 m ² / g and a porosity value of 0.27-0 , 42, is characterized by increased chemical resistance in aggressive environments and its use in plasticized compositions for the production of various products helps to increase their physical and mechanical properties.

Claims (2)

1. Suspension polyvinyl chloride with a Fikentcher constant Kf = 77-88, which is a powder consisting of porous opaque particles, characterized by a specific surface area of 1.0-4.0 m ² / g and a porosity value of 0.27-0.42, increased chemical resistance in aggressive environments obtained by water-suspension polymerization of a reaction mixture containing vinyl chloride, stabilizer, peroxide initiator, at an average polymerization temperature of 35-42 ° C and a stirrer rotation speed of 0.5-3.5 s ^-1 . 2. The use of suspension polyvinyl chloride according to claim 1 in plasticized compositions for the manufacture of materials with improved physical and mechanical characteristics.