DK168446B1 - Styrene / butadiene graft copolymer latex - Google Patents

Abstract

1. A styrene/butadiene graft copolymer latex obtained by emulsion polymerization in the presence of 1 to 6% by weight of a conventional fat soap and/or resin soap as emulsifier and >= 0.3% by weight of a conventional molecular weight regulator for the polymer, each percentage being based on the total monomers, and characterized by the following features : a) the emulsion polymerization is carried out by a semi-continuous emulsion-feed process ; b) the graft copolymer is composed of 35 to 65% by weight of the graft base (A) which in turn is composed of the graft base (A1) and the grafted-on component (A1), and 35 to 65% by weight of component (B) grafted on in the final step ; c) the graft base (A) is obtained in two polymerization steps ; in the first step, a polystyrene nucleating latex is obtained whose solid (A1) is 1 to 20% by weight, based on the graft copolymer ; the component (A2) of the graft base (A), which is grafted on in the second step, is composed of 86 to 95% by weight of repeating units which are obtained by polymerization of styrene, and 5 to 14% by weight of repeating units which are obtained by polymerization of 1,3-butadiene ; feeding of the emulsifier during grafting being accompanied by intensive stirring in order to avoid the formation of new particles ; d) the component (B) of the graft copolymer, which is grafted on in the final step, is composed of 62 to 70% by weight of repeating units which are obtained by polymerization of styrene, and 30 to 38% by weight of repeating units which are obtained by polymerization of 1,3-butadiene ; feeding of the emulsifier during grafting being accompanied by intensive stirring in order to avoid the formation of new particles : e) the parameters in the preparation of the graft copolymer latex are selected such that the latex particles have an average diameter, determined by surface titration, of 120 to 300 nm.

Description

DK 168446 B1

According to the prior art, latex foam is usually produced in such a way that from a rubber latex and an amplifier latex, ie. the latex from a reinforcing polymer, by mixing the latexes a reinforced rubber latex, the reinforced 5 kaut s yoke component, is obtained. From this as well as an effective amount of a vulcanizing agent and usual additives, a heat-vulcanizable mass is obtained. This is foamed with air or another gas, a gelling agent such as e.g. sodium silicofluoride, is then gelled and vulcanized in the heat (DE-10 Patent No. 10 56 364, DE Publication No. 14 70 810). The gelation occurs at room temperature in the infrared region or during the heating phase of the vulcanization. In the non-gel method, special measures for the gelling are voided. The latex foam thus produced has a cellular structure.

Latex foam must have a good property image which can be described by the following property combination: a) High elasticity in the temperature range from 20 to 70 ° C, ie. in this temperature range, after longer compression, the 20 compression set residue (compression set) must be the lowest possible (DIN 53 572).

b) High tensile strength and high elongation at break (DIN 53 571).

c) For given impression hardness, the room weight must be as small as possible (DIN 53 576, economy). You can also say: At the given room weight, the indentation hardness (shock hardness) must be as high as possible.

The described property combination is realized only imperfectly in the prior art.

DE Patent Specification No. 24 55726 proposes a styrene / butadiene graft copolymer to enhance a synthetic rubber. In addition, the styrene / butadiene graft copolymer is mixed with the DK 168446 B1 2 synthetic rubber. The mixtures thus obtained are suitable for the production of shoe soles as well as electrical insulation materials. Thus, contrary to the prior art described above, no latexes are mixed. The styrene / butadiene graft copolymer is obtained by emulsion polymerization following a two-step batch process.

It is the object of the present invention to provide an amplifier latex by which the described combination of properties can be better realized than in the prior art.

10 The task was surprisingly solved as stated in the claims.

This invention relates to an styrene / butadiene pod copolymer latex suitable as an amplifier latex which is characterized by structural and process parameters as follows: a) obtained by emulsion polymerization following a basic known, semi-continuous emulsion process method in the presence of 3, to 5 mass% of an ordinary fat soap and / or resin soap as an emulsifier and s 0.3, in particular s 0.2 mass% of an ordinary compound which regulates the molecular weight of the polymerate, in each case based on the total monomers; b) the graft copolymer is comprised of 35 to 65% by weight graft (A), which in turn consists of graft (A1) and grafted portion (A2), and 35 to 65% by weight of a grafted portion (A) in the final step ( B) c) the graft substrate (A) is obtained in two polymerization steps; in the first step, a polystyrene chimlatex whose solids content (Al) is 1 to 20 is obtained, in particular 5 to 15% by weight, calculated on the graft copolymer; the proportion (A2) of the graft substrate (A2), which is grafted in the second step, consists of 86 to 95 mass% repeating units obtained by polymerization of styrene and 5 to 3 mass% repeating units obtained by polymerization of 1,3-butadiene; at the inlet of the emulsifier during grafting, it is stirred intensively to avoid the formation of new particles; d) the proportion (B) of the graft copolymer polymer grafted in the last step consists of 62 to 70 wt% repeating units obtained by polymerization of styrene and 30 to 38 wt% repeating units obtained by polymerization of 1, 3-butadiene; at the inlet of the emulsifier during grafting, it is stirred intensively to avoid the formation of new particles; E) the parameters in the preparation of the graft copolymer latex are basically selected in a known manner such that the latex particles have a mean diameter (soap titration) in the range of 120 to 300 nm.

The emicon tinous straight emulsion process for preparing the styrene / butadiene graft copolymer latex is basically known (see, for example, U.S. Pat. No. 4,134,872).

The styrene / butadiene graft copolymer particles in the amplifier latex according to the invention exhibit relatively hard and soft regions with relatively high, relatively low glass transition temperature, due to features b) to d). The particles can be described in a simplified manner as follows:

They consist of a relatively hard core (graft substrate) and a relatively soft shell with relatively high and low Tg, respectively.

The surface titration to determine the mean diameter of the styrene / butadiene graft copolymer particles occurs as described in J. Paint Techn. 47 (1975) 41, right column, last paragraph et seq.

The styrene / butadiene graft copolymer latex of the invention is generally used as an amplifier latex for the manufacture of the 30-reinforced kaut s yoke component. It usually has the following characteristics: 1. it is obtained through the following measures: 1.1 a rubber latex is mixed with an amplifier latex (latex of a reinforced polymer: solids: 2 to 30, in particular 5 to 5 25 parts per hour): 1.2 the mixture of latexes is evaporated to a solids content of α 55, especially s 60 mass%; 2. The rubber latex is an NR latex or an SBR latex subjected to measures causing agglomeration of the 10 kaute yoke particles, or a mixture of an NR latex and an SBR latex subjected to measures causing agglomeration. of the rubber particles; 3. The SBR latex is not carboxylated; it is obtained by emulsion polymerization in the presence of a conventional fatty soap and / or resin soap as an emulsifier, SBR contains 15 to 35, in particular 20 to 30 mass% repeating units obtained by polymerization of styrene; 4. The reinforced kaut s yoke component at a solid content of 68 mass% exhibits a viscosity of α 2,500, in particular α 2,000 20 mPas, determined in the Brookfield viscometer (spindle III, 30 rpm, 20 ° C).

The measures for agglomerating the rubbery particles in the SBR latex are known (see, for example, DE-PS Nos. 12 13 984 and Nos. 26 45 082). 1

By vulcanizing agents for preparing the heat vulcanizable mass is understood the systems of known vulcanization systems. A preferred vulcanization system contains sulfur in combination with the usual accelerators. The amount of the vulcanizing agent is directed to the other blending components and can be easily determined by simple orienting experiments.

Conventional additives for preparing the heat-vulcanizable mass are e.g. fatty soaps and resin soaps (they may already be present in the reinforced chewing gum component in an amount sufficient for the further processing of the vulcanizable mass), aging and light preservatives, thickeners, e.g. carboxymethyl cellulose, and fillers, e.g. chalk, kaolin and starch.

The invention is illustrated by the following examples. In these, part (T) means mass parts and percent (%) mass percent.

The comparative excerpts, which are not according to the invention, are denoted by uppercase letters.

The average particle diameter of the latexes described below was determined as indicated above.

The viscosities of the reinforced chewing gum components were determined in Brookfield viscometer (spindle III, 30 rpm, 20 ° C).

Preparation of the amplifier latexes 1 and A - C: 1 2 3 4 5 6 EXAMPLE 1.

2 (styrene / butadiene graft copolymer latex according to the invention): 3 In a polymerization reactor, an emulsion of 84 T was fully de-salted water, 0.2 T potassium oleate (solid, present as 5 17% aqueous solution), 0 , 1 T potassium carbonate, 0.015 T of the tetrasodium salt of ethylene diamine tetraacetic acid, 10 T styrene and 0.15 T ammonium peroxodisulfate heated for 1-2 hours to 70 ° C. Thereby a polystyrene seed latex with an average particle diameter of 40 nm was obtained.

6 DK 168446 B1

To this material were added the following streams at 75 ° C: 1) Mixture of 19 T full of salted water and 4 T potassium oleate (solid, present as 17% in aqueous solution), addition time 5 hours (constant flow rate).

2) Dissolve 1.35T ammonium peroxodisulfate in 5T fully salted water, addition time 6 hours (constant flow rate).

3) Mixture of 45 T styrene / l, 3-butadiene (mass ratio 89/11) and 0.06 T tert-dodecyl mercaptan, to set time 2.5 hours 10 (constant flow rate).

4) Mixture of 45 T styrene / 1,3-butadiene (mass ratio 67/33) and 0.09 T tert-dodecyl mercaptan, addition time 2.5 hours (constant flow rate).

The addition of streams 1-3 was started simultaneously. After 15 2.5 hours (completion of the first inoculation stage), stream 4 was started.

The styrene / buta-diene graft copolymer latex obtained after completion of the second stage step had a solids content of approx. 501 and an average particle diameter of 220 nm.

EXAMPLE A

(styrene / butadiene graft copolymer latex):

The example corresponds to Example 1 in the mass ratio of the total monomers used (styrene / 1,3-butadiene = 80/20) to the other manufacturing parameters, but streams 3 and 4 were replaced with the following stream: 3) 90 T styrene / 1,3-butadiene (mass ratio 70/20) and 0.15 T tert-dodecylmercaptan, addition time 5 hours (constant flow rate).

Addition of streams 1-3 was started simultaneously.

The styrene / butadiene-podeco-polymerized latex obtained after the inoculation step had a solids content of approx. 50% and 5 an average particle diameter of 200 µm.

EXAMPLE B

(styrene / butadiene graft copolymer latex):

The example is similar to Example 1, but stream 4 was replaced with the following stream: 4) Mixture of 45 T styrene / 1,3-butadiene (mass ratio 72/28) and 0.09 T tert-dodecylmercaptan, addition time 2.5 hours (constant flow rate).

The styrene / butadiene graft copolymerate latex obtained after the second graft stage had a solids content of approx. 50% and an average particle diameter of 210 nm.

EXAMPLE C

(polystyrene latex):

The example is similar to Example 1, but streams 3 and 4 were replaced with the following stream: 1 3) Mixture of 90 T styrene and 0.15 T tert-dodecyl mercaptan, addition time 5 hours (constant flow rate).

The addition of streams 1-3 was started simultaneously.

The polystyrene latex obtained after polymerization had a solids content of approx. 50% and an average particle diameter of 200 nm.

For the SBR latex liners:

The latex was prepared in a known manner by Redox polymerization following the following recipe: 5 120 T of completely desalted water, 2.7 T of potassium oleate (calculated as 100% yeast), 0.5 T of a condensation product of formaldehyde and naphtha-1 -sulfonic acid , 0.29 T potassium chloride, 10 31 T styrene, 69 T 1,3-butadiene.

After 65% reaction of the monomers, polymerization was discontinued. The resulting SBR latex was subjected to the measures specified in DE-PS 12 13 984 for agglomeration of the rubber particles. The average particle diameter was then 240 nm. Res tmonomer eme was separated in known manner. The polymerization contained 26% repeating units produced by polymerization of styrene (IR analysis).

Preparation of the Reinforced Rubber Components 1 and A - C: The 20 SBR latex was in each case mixed with one of the amplifier latexes 1 and A - C (solids: 20 T phr). The resulting mixture of the latexes was evaporated to a solids content of 70%.

With a 68% solids content, the reinforced Kaut-25's yoke components exhibited the following viscosities: 1: 1,400 mPa's. A: 1,200 mPa * s. B: 1,300 mPa * s.

C: 1,350 mPa'S.

9 DK 168446 B1

Preparation of the vulcanizable masses 1 and A - C and the latex foams (sample layers) 1 and A - C:

The vulcanizable masses were prepared according to the following recipe (solids): 5 100 T of one of the reinforced chewing gum components 1 and A - C, 0.5 T potassium oleate (addition as 17% aqueous solution), 0.25 T carboxymethyl cellulose (addition as 2.5% aqueous solution).

Prior to foaming, the vulcanizable masses were completed by adding a 50% dispersion of the following vulcanization system (solids): 2 T sulfur, 1 T zinc diethyl dithiocarbamate, 1 T zinc-2-mercaptobenzothiazole, 1 T diphenylguanidine, 3 T zinc oxide, 0.5 T potassium oleate (addition as 17% aqueous solution), 1 T antioxidant.

Air was whipped into the vulcanizable masses with a foamy machine. To the resulting wet foams (about 130 g / l) were added 2 T sodium silicofluoride, which was present as 25% aqueous solution, and poured into heating molds, by gelling in the heating phase and subsequent vulcanization at 100 ° C / For 30 minutes, latex foams 1 and A - C. were obtained. They were washed with water, dried at 75 ° C / 16 h (room weight 100 g / l) Qg characterized as shown in the following table.

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Claims (4)

1. The styrene / butadiene graft copolymer latex obtained by emulsion polymerization in the presence of 1 to 6 mass% of a conventional fat soap and / or resin soap as emulsifier and s 0.3 mass% of a conventional compound which regulates the molecular weight of the polymerate. each mass% being based on the total monomers, characterized in that: a) the emulsion polymerization is carried out following a semi-continuous emulsion flow process; b) the graft copolymer consists of 35 to 65 mass% graft substrate 15 (A), which in turn consists of graft substrate ) and grafted portion (A2), and 35 to 65% by mass of a grafted portion (B) in the last step, c) the graft substrate (A) is obtained in two polymerization steps; in the first step, a polystyrene germ latex whose solids content (A1) is 1 to 20 mass% is obtained, based on the graft copolymer; the proportion (A2) of the graft substrate (A2) grafted in the second step consists of 86 to 95 mass% repeating units obtained by polymerization of styrene and 5 to 14 mass% repeating units obtained by polymerization of 1.3 Butadiene; at the inlet of the emulsifier during grafting, it is stirred intensively to avoid the formation of new particles; (d) the proportion (B) of the graft copolymer polymer grafted in the last step consists of 62 to 70 wt% repeating units obtained by polymerization of styrene and 30 to 38 wt% repeating units obtained by polymerization of 1, 3-butadiene; upon feeding the emulsifier during grafting, intensively stirred to prevent the formation of new particles; e) the parameters for the preparation of the graft copolymer latex are selected such that the latex particles have a mean diameter, as determined by surface titration, of 120 to 300 nm. The styrene / butadiene graft copolymer latex according to claim 1, characterized in that: (f) the graft copolymer consists of 45 to 60 weight percent graft (A) and 40 to 55 weight% of the proportion (B) grafted in the last step. The styrene / butadiene graft copolymer latex according to claim 1 or 2, characterized in that: g) the grafted portion (A2) of the graft substrate (A) consists of 87 to 93 wt% repeating units obtained by polymerization of styrene, and 7 to 13 mass% repeating units 15 obtained by polymerization of 1,3-butadiene? (h) the proportion (B) of the graft copolymer which is grafted in the last step consists of 65 to 69 mass% repeating units obtained by polymerization of styrene and 31 to 35 mass% repeating units obtained by polymerization of 1,3-buta - 20 done. The styrene / butadiene graft copolymer latex according to any one of claims 1 to 3, characterized in that i) the latex particles have an average diameter of 150 to 250 nm. 25