JPS586741B2 - Blocks of latex materials - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in block copolymer latex compositions comprising a conjugated diolefin and a monovinyl-substituted aromatic compound.

More specifically, the present invention relates to a composition with improved film-forming properties of a block copolymer latex composed of a conjugated diolefin block and a monovinyl-substituted aromatic compound block obtained by a solution polymerization method.

Synthetic rubber latexes such as styrene-ptadiene 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 characteristic solution polymerization type synthetic rubbers have been produced, and attempts to use these as latexes have been surpassed.

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, which can be used as is, but can be concentrated by creaming, centrifugation, or other operations if necessary.

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

These have the general formula B{-A-B)n or (A-B}-nA or (A-B)mX (where B is a block consisting essentially of a military diolefin polymer, and A is an essentially monovinyl-substituted aromatic block consisting of a group compound polymer, n is an integer of 2 to 10, m is 3 to
an integer of 7, X is m polymer chains A-B bonded,
It is a residue derived from a polyfunctional compound).

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

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 is used in paint binders, latex-added asphalt, cement compounding agents, etc.

However, an aqueous latex prepared by using such a block copolymer together with an emulsifier such as a higher fatty acid salt, a rosinate salt, or a disproportionated rosinate salt has a high minimum film formation temperature (hereinafter abbreviated as MFT). However, the disadvantage is that it is not possible to form a film under natural conditions.

The MFT referred to here is the professional software engineer (Thomas F.
The temperature gradient plate method (J
Our own of Applied Polymer
Science, Vol. 4, pp. 81-85)
This is the film-forming temperature measured by.

Until now, internal plasticization, external plasticization, temporary plasticization, etc. have been used to improve film formability.

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 film 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, the block copolymer exhibits a softening phenomenon due to the plasticizing effect during the latex formation process, 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 plasticization must be emulsified in water and then absorbed into the block copolymer particles by diffusion through the water, and the plasticization must be sufficient to form a homogeneous latex film at low temperatures. Therefore, a large amount of plasticizer is required for a long field.

In particular, the use of a large amount of plasticizer is not preferred 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, aids film formation, and improves the mechanical properties of the film by evaporating relatively quickly after the film is formed. Because plasticizers are expensive and large amounts of organic solvents are 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 MM
In order to improve the film forming properties of MMA in a blend system of ethyl acrylate (abbreviated as A) and low MFT (hereinafter abbreviated as EA), the EA content in the blend system must be 40% by weight or more. (Journal of Applied P
Olymer Science, Volume 14, Page 81 (1960)).

In addition, in a blend system of polystyrene latex and natural rubber latex, in order to improve the film forming properties of the polystyrene latex, the solid content of natural rubber latex is 80 parts by weight per 100 parts by weight of the total solid content of the latex.
Even if a large amount (parts by weight) is blended, the film forming properties of polystyrene latex are not improved at all.

The present inventors added natural rubber latex or synthetic rubber latex to a block copolymer latex consisting of a conjugated diolefin and a monovinyl-substituted aromatic compound as a solid content based on 100 parts by weight of the total solid content of the block copolymer latex. It was discovered that the film-forming properties of the block copolymer were improved with a surprisingly small amount of blending of 20 parts by weight compared to the MMA-EA blend system or the polystyrene-natural rubber blend system. Reached.

The present invention is directed to (A) a block copolymer comprising a conjugated diolefin obtained by a solution polymerization method and a monovinyl-substituted aromatic compound, having a molecular weight of 5,000 to 500,000 and a monovinyl-substituted aromatic compound content of 10 to 70% by weight; (B) natural rubber latex or synthetic rubber latex, or A block copolymer latex composition with improved film-forming property, characterized in that the mixture thereof is contained in 15 to 100 parts by weight as a solid content based on 100 parts by weight of the total solid content of the block copolymer latex. It provides:

The block copolymer used in the present invention has the general formula A-B-A or (A-B)n or B-(A-B)n or (A-B)+nA or (A-B)mX (formula (A, B, X, n and m have the same meanings as above) and can be polymerized by a living anionic polymerization method using an alkali metal-based initiator.

Monovinyl-substituted aromatic compounds include styrene, 0- or p-vinyltoluene, vinylxylene, ethylstyrene, isopropylstyrene, ethylvinyltoluene,
Examples include tertiary butylstyrene, diethylstyrene, and vinylnaphthalene, and two or more of these can also be used in combination.

As the conjugated diolefin, 1,3-putadiene,
Examples include 3-pentadiene, isoprene, and 2,3-dimethylptadiene, and two or more of these can also be used in combination.

Preferred combinations are 1,3-ptadiene 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 tin 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 obtained latex.

The content of the monovinyl-substituted aromatic compound polymer block in the block copolymer can be selected within the range of 10 to 70% by weight based on the total polymer, and outside this range, it has characteristics as a thermoplastic elastomer. This is not desirable because it results in a lack of

As the polymer solution for producing the block copolymer latex, the polymerization reaction solution may be used as it is, or the solid rubber of the block copolymer may be mixed with benzene, toluene,
It may be used by dissolving it in a solvent such as quinolene, cyclohexane, cyclooctane, chloroform, carbon tetrachloride, trichlene, 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 at least one of higher fatty acid salts (e.g., potassium oleate, sodium laurate, etc.), rosinate salts, or disproportionated rosinate salts, and the amount used is determined in accordance with the block. 0 per 100 parts by weight of polymer
．． 5 to 15 parts by weight, preferably 1 to 8 parts by weight.

When using higher fatty acid salts, rosinate salts, or disproportionated stodate salts of the emulsifier, they may be directly dissolved in water and used.Also, higher fatty acids, or Dissolve rosin acid or disproportionated rosin acid, use an alkaline aqueous solution (e.g., aqueous sodium hydroxide solution, etc.) as a dispersion medium, and mix and emulsify the polymer solution and the aqueous solution to obtain a higher fatty acid salt or rosin acid. Salts or disproportionated rosinate salts may be generated and used.

The reason why the amount of the emulsifier is limited is that if it is less than 0.5 parts by weight, it is difficult to emulsify, and if it is more than 15 parts by weight, foaming becomes intense during the solvent removal operation, making the operation difficult, which is not preferable.

Furthermore, in order to prevent precipitation and coagulation of latex particles during emulsification, desolvation, and concentration, and further improve the mechanical stability of the produced latex, in addition to the emulsifier, the general formula R1-(0-R2 )+nlOH, and R1 has 8 or more carbon atoms
18 alkyl group, or alkyl group having 8 to 12 carbon atoms
alkyl phenyl group, R2 is an alkylene group having 2 to 5 carbon atoms, and n' is an integer of 3 to 50), such as polyoxyethylene nonyl phenyl ether,
Polyoxyethylene lauryl ether, polyoxyethylene nonyl phenyl ether phosphate, polyoxyethylene glopylene nonyl phenyl ether phosphate, etc. may be used in combination.

The amount of the compound represented by the above general formula used is 0.5 to 15 parts by weight, preferably 2 to 8 parts by weight, based on 100 parts by weight of the block copolymer.

In the present invention, any known emulsifying machine may be used as long as it has a sufficiently strong emulsifying ability.

For example, there are homomixers, homogenizer disper mills, and colloid mills, and two types of emulsifying machines can be used in combination as necessary.

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 creaming, centrifugation, and water evaporation. In particular, concentration using a centrifuge is efficient and
This method is preferred because it is highly reproducible.

In the present invention, the compounding agent for improving the film-forming properties of the latex of the block copolymer includes natural rubber latex, synthetic rubber latex, or a mixture thereof, and the amount of the latex used is equal to that of the block copolymer latex. For 100 parts by weight of total solid content, the solid content is 1
5 to 100 parts by weight, preferably 20 to 60 parts by weight.

If it is less than 15 parts by weight, the effect of improving film formability is poor, and 1
If the amount is more than 0.00 parts by weight, the mechanical strength of the film obtained from the latex will decrease and the characteristics as a thermoplastic elastic body will be lost, which is not preferable.

The synthetic rubber latex is not limited as long as it has film-forming properties at room temperature.For example, styrene-butadiene copolymer latex, butadiene polymer latex,
Isoprene polymer latex, styrene-butadiene-vinylpyridine copolymer latex, butadiene-acrylonitrile copolymer latex, butadiene-methyl methacrylate copolymer latex, chloroprene polymer latex, isoprene-isobutylene copolymer latex, etc. If used, these may be modified with a carboxyl group or a hydroxyl group.

The block copolymer latex composition with improved film-forming properties of the present invention includes preservatives, plasticizers, antifoaming agents, antifreeze agents,
Corrosion inhibitors, wetting agents and other conventional auxiliary substances can be included in the amounts commonly used.

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 to active lithium in a 15 wt% n-hexane solution containing 41 g of a monomer mixture of 1,3-butadiene and styrene in a weight ratio of 50:50. After polymerizing at 60°C for 4 hours to copolymerize most of all monomers, add 1 mmol of 3-butadiene to styrene in a weight ratio of 65:35 to the active copolymer solution. 1 containing 59 g of polymer mixture
A 5% by weight n-hexane solution was added and polymerized at 70°C for 2 hours, and further polymerized at 85°C for 1 hour to copolymerize almost all of the additional monomers.
-G-tert-butyl-p-cresol was added and 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 elastomer consisting of putadiene and styrene.
Its molecular weight is approximately 100,000.

For 100 parts by weight of a toluene solution (polymer concentration 10% by weight) of the block copolymer, 100 parts by weight of an aqueous sodium rosinate solution containing 5 parts by weight of sodium Jum rosinate per 100 parts by weight of the block copolymer. The components were mixed and emulsified using 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.

Natural rubber latex (solid content 59%) was added in varying amounts from 20 to 80 parts by weight in terms of solid content to 100 parts by weight of the total solid content of the concentrated latex, and a uniform dispersion was obtained by simple stirring with a stirring rod. .

The MFT of the latex composition thus obtained was determined by the temperature gradient plate method proposed by Protutzman et al., and the 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 The emulsification was carried out by adding 3 parts by weight of polyoxyethylene nonyl phenyl ether (average degree of polymerization: 15) to 100 parts by weight of the block copolymer in addition to the emulsifier sodium rosinate in Example 1. A concentrated latex was produced in the same manner as in Example 1 (solid content concentration 57% by weight).To 100 parts by weight of the total solid content of the concentrated latex, a carboquine styrene-butadiene copolymer latex (manufactured by Asahi Dow Co., Ltd.) was added. , Dow Latex DL
620, solid content 50% ± 1) from 20 to 8 in terms of solid content
They were added in small amounts up to 0 parts by weight and were made into a uniform dispersion by simple stirring.

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

Example 3 Rosin acid was dissolved in a toluene solution of the block copolymer of Example 1 in an amount of 5 parts by weight per 100 parts by weight of the block copolymer, and an equimolar amount of sodium hydroxide was added to this and the rosin acid.
An aqueous solution in which Jum was dissolved was mixed at a weight ratio of 1:1, and emulsified in the same manner as in Example 1 to obtain a solid content of 54% by weight.
A concentrated latex was produced.

Styrene-ptadiene copolymer latex (manufactured by Asahi Dow Co., Ltd., Dow Latex DL612, solid content 48% ± 1) is added from 20 to 80 parts by weight in terms of solid content, based on 100 parts by weight of the total solid content of the concentrated latex. A uniform dispersion was obtained by adding in small quantities and stirring easily.

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

Example 4 Emulsification was carried out in the same manner as in Example 1 except that disproportionated potassium rosin acid was used instead of sodium rosinate in Example 1 to produce a concentrated latex (solid content concentration 55
weight%).

Butadiene-methyl methacrylate copolymer latex (manufactured by Takeda Pharmaceutical Co., Ltd., Crossren 2M-34, solid content 48%) is added from 20 to 80 parts by weight in terms of solid content, relative to 100 parts by weight of the total solid content of the concentrated latex. A uniform dispersion was obtained by adding in small quantities and stirring easily.

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

Example 5 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 concentration 53% by weight).

Styrene-butadiene-pinylpyridine copolymer latex (manufactured by Japan Synthetic Rubber Co., Ltd., JSRO650, solid content 4 parts by weight) was added to 100 parts by weight of the total solid content of the concentrated latex.
0%) was added in varying amounts from 20 to 80 parts by weight in terms of solid content, and a uniform dispersion was obtained by simple stirring.

The same measurements as in Example 1 were carried out, and the results are shown in Table 5.

Example 6 A concentrated latex was produced in the same manner as in Example 1 except that a 20% block copolymer benzene solution was used instead of the 10% toluene solution of the block copolymer in Example 1 (solid content concentration 57% by weight), chloroprene polymer latex (manufactured by Showa Neoprene Co., Ltd., Neoprene Latex 571, solids content 50%) is 20 parts by weight in terms of solid content per 100 parts by weight of the total solid content of the concentrated latex.
80 parts by weight were added in varying amounts, and a homogeneous dispersion was obtained by simple stirring.

Measurements similar to those in Example 1 were carried out, and the results are shown in Table 6.

Comparative Example The same procedure as in Example 1 was repeated 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. (solid content concentration 53% by weight). Total solid content of the concentrated latex: 10
0 parts by weight, natural rubber latex (solid content 59%)
and carpoquinated styrene-butadiene copolymer latex (manufactured by Asahi Dow Co., Ltd., Dow Latex DL62
0, solid content 50% ± 1) were added in varying amounts from 20 to 80 parts by weight in terms of solid content, and MFT was applied in the same manner as in Example 1.
When measured, no decrease in MFT was observed.

The results are shown in Tables 7 and 8.

Claims (1)

[Claims] 1 (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 seeds and at least one emulsifier selected from higher fatty acid salts, rosinate salts, and disproportionated stomate salts; (B) 100 weight solids in the aqueous latex; Per part, solid content: 15~
A block copolymer latex composition with improved film-forming properties, characterized in that it contains 100 parts by weight of natural rubber latex, synthetic rubber latex, or a mixture thereof.