JPS586742B2 - Blocks of latex materials - Google Patents

Description

Detailed Description of the Invention The present invention aims to improve the film-forming properties of a block copolymer latex produced from an organic solvent solution of a block copolymer composed of a conjugated diolefin and a monovinyl-substituted aromatic compound obtained by a solution polymerization method. The present invention relates to a latex composition made of

Synthetic rubber latexes such as styrene-butadiene copolymer latexes are generally produced by emulsion polymerization and are practically used.

However, as a result of rapid advances in polymerization technology in recent years, a large number of distinctive solution polymerization type synthetic rubbers have been produced, and the use of these as latex has come to be considered.

The general method for producing latex from this type of solution-polymerized synthetic rubber is to add an emulsifier and water to a rubber polymerization solution or solid rubber dissolved in a suitable solvent to emulsify it. The solvent is removed from the resulting emulsion by stripping, flushing, etc.

Furthermore, the latex thus obtained is a so-called dilute latex, and can be used as is, but can be concentrated by creaming, centrifugation, or other operations as necessary.

One of the characteristic synthetic rubbers obtained by solution polymerization is a block copolymer in which monovinyl-substituted aromatic compound polymer blocks and conjugated diolefin polymer blocks are bonded alternately.

Such block copolymers have the general formula A-B-A, (A-B)n, B+(A-B)n, (A-B)+nA or (A-B)mX (where A is a block consisting essentially of a monovinyl-substituted aromatic compound polymer, B is a block consisting essentially of a conjugated diolefin polymer, n is an integer of 2 to 10, and m is 3 to
An integer of 7, X is a residue of a polyfunctional compound having m bonds.

These are called thermoplastic elastomers, and without the usual crosslinking treatment with sulfur compounds, etc., they exhibit high strength, elongation, and low residual strain comparable to ordinary vulcanized rubber.

These block copolymer latexes utilize their unique properties to be used in dip molded products, cast molded products, foam rubber, rubber thread, paper processing agents, carpet sizing agents, fiber processing agents, surface coating agents, and adhesives. It can be used in a wide range of applications, including paint binders, latex-added asphalt, and cement additives.

However, aqueous latexes prepared using such block copolymers together with emulsifiers such as higher fatty acid salts, rosinate salts, or disproportionated stodate salts have low film formation temperatures (hereinafter abbreviated as MFT). It has the disadvantage that it is expensive and cannot form a film under natural conditions.

The MFT referred to here is Protutzmann (Thomas F.
The temperature gradient plate method (J
Our own of Applied Polymer
Science Volume 4, Pages 81-85 (196
0)) is the film forming temperature measured by the above method.

Hitherto, internal plasticization, external plasticization, temporary plasticization, and the like have been used to improve film formation properties.

The internal plasticization method is a method of copolymerizing soft component monomers (monomers that form a homopolymer with a low glass transition temperature), and is a method of copolymerizing a soft component monomer (a monomer that forms a homopolymer with a low glass transition temperature). This method is inappropriate as a method for improving membrane properties.

The external plasticization method is a method that uses a plasticizer, and there are two ways to add it: when producing the latex or after producing it.

In the former case, during the process of making latex, the block copolymer exhibits a softening phenomenon due to the plasticizing effect, resulting in insufficient emulsification, resulting in only relatively large particles, and the emulsified particles may not reagglomerate. There were problems with the stabilization of latex, such as the fact that it was easy to wake up.

In the latter case, the plasticizer must be emulsified in water and then absorbed into the block copolymer particles by diffusion through the water, and the plasticizer must be sufficiently plasticized to form a homogeneous latex film at low temperatures. This inevitably requires a long period of time and a large amount of plasticizer.

In particular, the use of a large amount of plasticizer is undesirable because it significantly reduces the mechanical properties of the latex film.

Temporary plasticization is a method that acts as a plasticizer only when the film is formed, aiding the film formation, and evaporates relatively quickly after the film is formed, improving the mechanical properties of the film, but it is temporary. Because the plasticizer is expensive and a large amount of organic solvent is used, there are problems with worker health and safety, fire, and air pollution that need to be resolved.

Furthermore, for latexes with high MFT and poor film-forming properties at room temperature, a method of improving film-forming properties by blending latexes with low MFT is known.

For example, methyl methacrylate (hereinafter referred to as M
In order to improve the film forming properties of MMA in a blend system of ethyl acrylate (abbreviated as MA) and low MFT (abbreviated as EA hereafter), in the blend system, EA
The content must be at least 40% by weight (Journal of Applied
Polymer Science, Volume 14, Page 81 (1960)).

In addition, as shown in the examples below, in a blend system of polystyrene latex (latex produced in the same manner as the block copolymer latex in the present invention) and vinyl acetate polymer emulsion, the film-forming property of the polystyrene latex is Even if a large amount of vinyl acetate polymer emulsion is blended as a solid content of 80 parts by weight with respect to 100 parts by weight of the total solid content of the latex in order to improve the polystyrene latex, the film forming properties of the polystyrene latex are not improved at all.

The present inventors added a vinyl acetate polymer emulsion, a vinyl acetate copolymer emulsion, or a mixture thereof to a block copolymer consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound, so that the total solid content of the block copolymer latex was 100%. The film-forming property of the block copolymer latex can be improved by using a surprisingly small amount of blend as compared to the MMA-EA blend system or the polystyrene-vinyl acetate polymer blend system, where the solid content is 20 parts by weight based on the solid content. The present invention has been achieved based on the discovery that this can be improved.

That is, the present invention consists of (A) (a) a conjugated diolefin block obtained by a solution polymerization method and a monovinyl-substituted aromatic compound block, and has a molecular weight of 5000 to 500.
000, a block copolymer having a monovinyl-substituted aromatic compound content of 10 to 70% by weight, and at least an emulsifier selected from higher fatty acid salts, rosinates, and disproportionated rosinates. (B) a solid content of 1 in the aqueous latex (A);
A block copolymer with improved film-forming properties characterized by blending a vinyl acetate polymer emulsion, a vinyl acetate copolymer emulsion, or a mixture thereof in an amount of 15 to 100 parts by weight as a solid content per 00 parts by weight. A latex composition is provided.

The block copolymer used in the present invention has the general formula AB
-A, (A-B)n, B-(A-B)n, (A-B)1
nA or (A-B)mXC (in the formula A, B, can do.

Monovinyl-substituted aromatic compounds include styrene, o- or p-vinyltoluene, vinylxylene, ethylstyrene, inglobylstyrene, ethylvinyltoluene,
Examples include tert-butylstyrene, diethylstyrene, and vinylnaphthalene, and two or more of these can also be used in combination.

Conjugated diolefins include 1,3-ptadiene, 1,
Examples include 3-pentadiene, isoprene, and 2,3-dimethylbutadiene, and two or more of these can also be used in combination.

Preferred combinations are 1,3-butadiene and styrene and isoprene and styrene.

Such a block copolymer can be produced by sequentially polymerizing monomers block by block in the presence of the initiator, or by simultaneously charging two or more monomers with different copolymerization reactivity ratios. It can be obtained by a method of polymerizing to obtain a block copolymer, or a method of coupling a living block copolymer using the above-mentioned initiator.

The block copolymer represented by (A-B)mX is A
-B○ can be obtained by coupling a living block copolymer with a polyfunctional coupling agent.

For example, a tetrafunctional coupling agent such as silicon tetrachloride can be used.

The molecular weight of the block copolymer is 5,000 to 500,000. If the molecular weight is less than 5,000, the mechanical strength of the film obtained from the latex will be poor, and if it exceeds 500,000, the solution viscosity will become too high during emulsification, resulting in incomplete or difficult emulsification. This adversely affects the performance of the resulting latex.

The content of the monovinyl-substituted aromatic compound polymer block in the block copolymer must be selected within the range of 10 to 70% by weight based on the total polymer; outside this range, the characteristics as a thermoplastic elastomer is not fully demonstrated.

An example of a method for producing block copolymer latex is shown below.

That is, the polymer solution when producing the block copolymer latex may be the polymerization reaction solution as it is,
Further, the solid rubber of the block copolymer may be used by dissolving it in a solvent such as benzene, toluene, xylene, cyclohexane, cyclooctane, chloroform, carbon tetrachloride, trichloride, or methane dichloride.

It is generally preferable to use the polymer solution at a concentration of 5 to 50% by weight.

The emulsifier used in the present invention is a higher fatty acid salt (e.g.
at least one of potassium oleate, sodium laurate, etc.), rosinate, or disproportionated rosinate, and the amount used is not limited, but is based on 100 parts by weight of the block copolymer. It is preferable to use it in a range of 0.1 to 15 parts by weight.

When using a higher fatty acid salt, a rosin acid salt, or a disproportionated rosin acid salt of the emulsifier, they may be directly dissolved in water, or the higher fatty acid, rosin acid, or Dissolve the disproportionated rosin acid, use an alkaline aqueous solution (for example, an aqueous sodium hydroxide solution, etc.) as a dispersion medium, and when the polymer solution and the aqueous solution are mixed and emulsified, higher fatty acid salts, rosinate salts, or disproportionated rosin acids are dissolved. It is also possible to produce and use dilatate salts.

Furthermore, in order to prevent precipitation and coagulation of latex particles during emulsification, desolvation, and concentration, and to further improve the mechanical stability of the produced latex, in addition to the emulsifier, if desired, the general formula R1- (0-R2-}n/OH or (R1 in the formula is an alkyl group having 8 to 18 carbon atoms or an alkylphenyl group having an alkyl group having 8 to 18 carbon atoms, R
2 is an alkylene group having 2 to 5 carbon atoms, and n/ is an integer of 3 to 50.

Examples of such compounds include polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene nonyl phenyl ether phosphate, and polyoxyethylene glopylene nonyl phenyl ether phosphate. can.

In the present invention, any emulsifying machine may be used as long as it has a sufficiently strong emulsifying ability, such as a homomixer, a homogenizer, a disper mill, and a colloid mill. Machines can be used in combination.

Next, as a method for removing the solvent in the emulsion to obtain a dilute latex, methods include distillation by heating with a jacket;
Known desolvation techniques can be used, such as steam distillation by blowing steam directly into the emulsion.

The dilute latex thus obtained is usually 5 to 50%
It has a solid content concentration of about 100% by weight. Methods for converting this into concentrated latex with a higher solid content concentration include the creaming method, centrifugation method, and water evaporation method. Concentration using a machine is efficient and highly reproducible, so it can be said to be a preferable method.

In the present invention, the compounding agent for improving the film-forming properties of the latex of the block copolymer includes a vinyl acetate polymer emulsion, a vinyl acetate copolymer emulsion,
or a mixture thereof, and the amount of the emulsion used is 15 to 100 parts by weight, preferably 20 to 60 parts by weight as a solid content, based on 100 parts by weight of the total solid content of the block copolymer latex.

If it is less than 15 parts by weight, the effect of improving film formation properties is poor;
If the amount is more than 0.00 parts by weight, the mechanical strength of the film obtained from the latex will be significantly reduced, and the characteristics as a thermoplastic elastic body will be lost.

The vinyl acetate copolymer emulsion is not limited as long as it can form a film at room temperature, and examples include vinyl acetate-ethylene copolymer emulsion, vinyl acetate-maleic anhydride copolymer emulsion, and vinyl acetate-maleic ester copolymer emulsion. Polymer emulsion, vinyl acetate-acrylic acid copolymer emulsion, vinyl acetate-veov
Examples include a copolymer emulsion, vinyl acetate-vinyl chloride copolymer emulsion, and vinyl acetate-vinyl chloride-acrylic acid copolymer emulsion.

The film-forming improved block copolymer latex compositions of the present invention contain preservatives, plasticizers, defoamers, antifreeze agents, corrosion inhibitors, wetting agents and other materials in commonly used amounts. can be done.

The present invention will be explained below with reference to Examples, but these are not intended to limit the scope of the present invention.

Example 1 In a nitrogen gas atmosphere, n-butyllithium was added as active lithium to a 15 wt% n-hexane solution containing 41 g of a monomer mixture of 3-butadiene and styrene in a weight ratio of 50:50. After adding 1 mmol and polymerizing at 60°C for 4 hours to copolymerize most of all the monomers, add 1,3-butadiene to styrene in a weight ratio of 65:35 to the active copolymer solution. 1 containing 59g of body mixture
A 5% by weight n-hexane solution was added and the polymerization was carried out at 70°C for 2 hours, and then at 85°C for 1 hour. After almost all of the additional monomer was copolymerized, 1g of 2.6- as a stabilizer was added.
Di-tert-butyl-p-cresol was added, and n was dried.
- 100 g of final block copolymer was obtained by removing the hexane solvent.

This copolymer contains 40% by weight of styrene.
It is a thermoplastic elastic body made of butadiene and styrene.
Its molecular weight is approximately 100,000.

A toluene solution of the block copolymer (polymer concentration, 10
100 parts by weight of sodium rosinate was mixed with 100 parts by weight of a sodium rosinate aqueous solution containing 5 parts by weight of sodium rosinate per 100 parts by weight of the block copolymer, and the mixture was emulsified in a disper mill.

The produced emulsion was immediately charged into a toluene removal tank equipped with a heating jacket and heated to evaporate and remove toluene.

At this time, some water evaporates together with toluene, resulting in a solid content of 13
．． A dilute latex with a concentration of 5% by weight was obtained.

This is continuously charged into a cylindrical centrifuge, and approximately 12,000
A concentrated latex with a solid content of 55% by weight was obtained by rotating.

Vinyl acetate polymer emulsion (manufactured by Hoechst Synthesis Co., Ltd.,
Movinyl 50M, solid content 50%) is converted to 20% solid content.
A homogeneous dispersion was obtained by adding in small quantities up to 80 parts by weight and stirring briefly with a stirring rod.

For the latex composition thus obtained, the MFT was determined by the temperature gradient plate method proposed by Protutzmann et al., and a film was formed at 80° C., and the tensile properties of the film were determined.

The results are shown in Table 1 in comparison with the case of block copolymer concentrated latex alone.

Example 2 A concentrated latex was produced by emulsifying in the same manner as in Example 1 except that disproportionated potassium rosinate was used instead of sodium rosinate as the emulsifier in Example 1 (solid content concentration 55% by weight). .

To 100 parts by weight of the total solid content of the concentrated latex, add 20 to 80 parts by weight of vinyl acetate-ethylene copolymer emulsion (manufactured by Inu Nippon Ink Chemical Co., Ltd., Everdik EP-11, solid content 54%) in terms of solid content. A homogeneous dispersion was obtained by adding in small amounts up to 100% and stirring briefly.

Measurements similar to those in Example 1 were carried out, and the results are shown in Table 2.

Example 3 A concentrated latex was produced in the same manner as in Example 1 except that cyclohexane was used instead of toluene as the solvent in Example 1.

(Solid content 54% by weight).

Vinyl acetate-maleate ester copolymer emulsion (manufactured by Hoechst Synthesis Co., Ltd., Movinyl DM2H, solid content 5 parts by weight) was added to 100 parts by weight of the total solid content of the concentrated latex.
1%) was added in varying amounts from 20 to 80 parts by weight in terms of solid content, and each was briefly stirred to form a uniform dispersion.

Measurements similar to those in Example 1 were carried out, and the results are shown in Table 3.

Example 4 Instead of the block copolymer made of styrene and 1,3-butadiene produced in Example 1, a radial teleblock copolymer made of styrene and 1,3-butadiene (Solprene T, manufactured by Nippon Egystomer Co., Ltd.) was used. A concentrated latex was produced in the same manner as in Example 1, except that 414) was used (solid content concentration: 55% by weight).

Vinyl acetate-ethylene copolymer emulsion (manufactured by Sumitomo Chemical Co., Ltd., Sumiriki Flex 751, solid content 50%) was added to 100 parts by weight of the total solid content of the concentrated latex.
A uniform dispersion was obtained by adding 20 to 80 parts by weight in terms of solid content and stirring briefly.

Measurements similar to those in Example 1 were carried out, and the results are shown in Table 4.

Comparative Example 1 A concentrated latex was prepared in the same manner as in Example 1 except that a styrene polymer (Styron 683, manufactured by Asahi Dow Co., Ltd.) was used instead of the block copolymer consisting of styrene and 1,3-ptadiene in Example 1. was produced (solid content concentration 53% by weight).

Vinyl acetate polymer emulsion (manufactured by Hoechst Synthesis Co., Ltd.,
Movinyl 50M, solid content 50%) in solid content equivalent to 20
80 parts by weight of MF was added in the same manner as in Example 1.
When T was measured, no decrease in MFT was observed.

The results are shown in Table 5.

As described above, a latex composition comprising a block copolymer latex comprising a conjugated diolefin and a monovinyl-substituted aromatic compound of the present invention and a vinyl acetate polymer emulsion, or a vinyl acetate copolymer emulsion, can be prepared by combining the block copolymer latex with a vinyl acetate polymer emulsion. The film-forming property of block copolymer latex is extremely effectively improved without impairing its characteristics.

Claims (1)

[Claims] 1 (A) (a) A block copolymer consisting of a conjugated diolefin block and a monovinyl-substituted aromatic compound block obtained by a solution polymerization method, with a molecular weight of 5,000 to 500,000 and a monovinyl-substituted aromatic compound content of 10 to 70% by weight. An aqueous latex containing at least one kind and at least one kind of emulsifier selected from higher fatty acid salts, rosinate salts, and disproportionated rosinate salts;
B) A vinyl acetate polymer emulsion, a vinyl acetate copolymer emulsion, or a mixture thereof is blended in an amount of 15 to 100 parts by weight as a solid content per 100 parts by weight of solid content in the aqueous latex (A). A block copolymer latex composition with improved film forming properties.