JPS61166811A - Production of modified vinyl ester-ethylene copolymer - Google Patents

Abstract

PURPOSE:To produce the titled copolymer having improved characteristics, facilitating the precipitation, washing and drying of the polymer, by adding a vinyl monomer having a specific solubility coefficient to a vinyl ester-ethylene copolymer latex. CONSTITUTION:(A) A copolymer latex prepared by the emulsion polymerization of a mixture of a vinyl ester (e.g. vinyl formate) and ethylene at a weight ratio of 4:6-9:1 is added with (B) a vinyl monomer having a solubility coefficient to the component A of >=8.5 (e.g. acrylic acid), and the obtained suspension system is subjected to the graft-polymerization preferably at 60-130 deg.C to obtain the objective copolymer.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for producing a vinyl ester/ethylene copolymer, and more specifically to a vinyl ester/ethylene copolymer latex obtained by emulsion polymerization. The present invention relates to a method for producing a vinyl ester/ethylene copolymer having improved properties in which vinyl monomers are polymerized in the presence of a polymer and the polymerization is completed in a suspension system.

[Prior art and its problems]

The copolymer of vinyl ester and ethylene is highly elastic,
It has excellent durability and good compatibility with other types of polymers.
It is used alone or in combination with other polymers as rubber parts, wire covering materials, waterproof sheets, etc. Vinyl ester/ethylene copolymers can be produced by bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization, but for molding materials, suspension polymerization and emulsion polymerization are carried out on an industrial scale. ing.

The greenhouse method is widely used because it is easy to recover, wash, and dry the polymer after the reaction. On the other hand, in the emulsion polymerization method, the amount of ethylene dissolved by the emulsifier is greater than that in the suspension polymerization method even at the same ethylene saturation pressure, so the ethylene content in the product can be increased. In addition, it has characteristics such as fast reaction rate, good productivity, and the ability to obtain copolymers with large molecular weights, so it is suitable for rubber applications where mechanical strength and filler filling ability are important, and highly filled polyvinyl chloride ( It is suitable for applications such as PVC) compositions.

However, the emulsion polymerization method requires a step of recovering the polymer from latex. Generally, coagulating agents such as inorganic salts and acids are added to latex for salting out, and then washing is performed to remove impurities such as coagulants and emulsifiers. However, the highly sticky rubber-like vinyl ester/ethylene copolymer Due to its viscosity, it was very difficult to precipitate, wash, dehydrate and dry the latex from the latex. Impurities such as emulsifiers and coagulants tend to remain in the polymer, increasing the water absorption of the vinyl ester/ethylene copolymer.
Due to these problems, such as poor electrical insulation, there was a need for a method that could reduce the negative effects of impurities in the polymer while taking advantage of the characteristics of emulsion polymerization.

Vinyl ester/ethylene copolymers with a vinyl ester content of 90 to 40%, which are used for rubber applications and PvC blend applications, are extremely sticky at temperatures above room temperature, and vinyl ester/ethylene copolymer latexes cannot be coagulated at temperatures above 50°C. When the polymer particles are coagulated using a coagulant by a known method at a certain temperature, a lump of polymer particles is obtained. In addition, even if a coagulant is added at a temperature below 50°C, the polymer may not completely precipitate and the waste liquid remains cloudy, or many times the amount of coagulant is required to completely precipitate the polymer. shall be. As a measure to improve this, the
No. 0, Special Publication No. 44-23623, Japanese Patent Publication No. 56-201
No. 515 describes a method of adding an inorganic compound to a vinyl ester/ethylene copolymer latex to prevent the precipitated polymer from sticking. Also, special public service 1977-13
No. 626 describes a method in which a hard resin is added after coagulating latex to prevent the polymer from sticking.

[Problem that the invention seeks to solve]

Although the above proposal can prevent polymer sticking, there is a problem that the addition of these anti-stick agents reduces the transparency and thermal stability of the vinyl ester/ethylene copolymer, and the addition of these anti-stick agents reduces the transparency and thermal stability of the vinyl ester/ethylene copolymer. Since the addition remains the same, impurities in the polymer will not be reduced and the electrical properties and water resistance of the vinyl ester/ethylene copolymer will not be improved.

For these reasons, while maintaining the characteristics of the emulsion-polymerized vinyl ester/ethylene copolymer such as high mechanical strength and high filler filling capacity, it is possible to improve the negative effects on physical properties caused by residues of emulsifiers and coagulants, and to improve the polymer properties. There is a need to simplify the precipitation, washing and drying steps.

(Means for solving the problem) As a result of various studies, the present inventors added and polymerized a polar vinyl monomer in the presence of vinyl ester/ethylene copolymer latex, and the reaction system was treated with a coagulant. It was discovered that by inverting the phase from an emulsion system to a suspension system and completing the polymerization in the suspension system without using a polymer, impurities in the polymer can be reduced and polymer precipitation, washing and drying can be facilitated, and the present invention has been made based on the present invention. Reached.

That is, the present invention provides vinyl ester and ethylene in a weight ratio of 4:6 to 9:1, and a solubility coefficient of 8.5 or more in a vinyl ester/ethylene copolymer latex obtained by an emulsion polymerization method. The present invention provides a method for producing a vinyl ester/ethylene copolymer, which is characterized in that a monomer is added, the polymerization is then carried out under a graft polymerization process, and the polymerization is completed in a suspension system. .

The vinyl ester/ethylene copolymer latex has a weight ratio of vinyl ester to ethylene of 4=6 to 9:1, more preferably 5:5 to 8:2, and a Mooney viscosity of 5 to 60. It is a latex of a certain copolymer.

Such vinyl ester/ethylene copolymer latex is usually obtained by copolymerizing vinyl ester and ethylene in water containing an emulsifier using a water-soluble radical initiator and has a particle size of 108 m or less. Examples of vinyl esters that can be used include vinyl formate, vinyl propionate,
Examples include vinyl acetate, vinyl pivalate, and vinyl versatate. Of these, vinyl acetate is the most preferred, and half or less of the vinyl ester may be replaced with another vinyl monomer within the scope of the present invention. Alternatively, other polymers and polymer latexes may be used in combination with the vinyl ester/ethylene copolymer latex.

The vinyl ester content in the copolymer is 40-90% by weight, preferably 50-80% by weight. If the vinyl ester content is less than 40% by weight, the modified vinyl ester
The filler filling property of the ethylene copolymer is poor, the compatibility with other polymers, especially PvC, is poor, and if it exceeds 90% by weight, the elasticity is low and the cold resistance is poor.

Examples of emulsifiers used include anionic emulsifiers such as potassium oleate, sodium lauryl sulfate, sodium dodecylbenzenesulfonate, sodium alkyl diphenyl ether disulfonate, and sodium polyoxyethylene alkyl ether sulfate; polyoxyethylene lauryl ether, polyoxyethylene nonylphenyl ether, Examples include nonionic emulsifiers such as polyoxyethylene propylene polymer; and cationic emulsifiers such as laurylamine acetate.

In addition to the emulsifier, a protective colloid such as methylcellulose, polyvinyl alcohol, or polyvinylpyrrolidone may be used as a dispersion aid. The amount of emulsifier added is such that the concentration of emulsifiers is below the critical micelle concentration in the reaction system, and is usually 0.001 to 0.0 per 100 g of latex after reaction.
5 mol% is preferred, such addition amount is 0.001 mol%
If the amount is less than 0.05, the vinyl ester/ethylene copolymer latex becomes stable during the reaction and polymerization does not proceed.
If it is more than mol%, the latex becomes too stable and the phase change from emulsion to suspension does not proceed smoothly.

A known water-soluble radical initiator is used as a polymerization initiator when synthesizing the vinyl ester/ethylene copolymer latex. Examples of such initiators include oxidizing agents alone such as potassium persulfate, ammonium persulfate, and hydrogen peroxide, or sodium sulfite, sodium hyposulfite, and monosulfuric acid.
It is used in combination with water-soluble reducing agents such as iron, ferrous nitrate, Rongalite, and thiourea.

The synthesis of vinyl ester/ethylene copolymer latex is carried out by the best known method.
The method described in No. 3732 is suitable.

The vinyl monomer added to the vinyl ester/ethylene copolymer described above has a solubility coefficient of 8.5 or more, and preferably the modified vinyl ester/ethylene copolymer obtained by polymerization has a solubility coefficient of 8.5. .5 to 9.5. The amount of the vinyl monomer added is usually 5 to 50% by weight, preferably 1% by weight of the modified vinyl ester/ethylene copolymer.
It is 5 to 30% by weight.

If the solubility coefficient of the vinyl monomer is lower than 8.5, when it is added to a vinyl ester/ethylene copolymer latex, the phase change from an emulsion system to a suspension system may not be carried out smoothly, and the transparency of the polymer may deteriorate. , oil resistance and compatibility with PVC decrease. Examples of these vinyl monomers include acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, and their lower alkyl esters; styrene, α
- Methylstyrene etc. and aromatic vinyls; vinyl halides such as vinyl chloride; vinyl esters such as vinyl acetate; vinyl cyanides such as acrylonitrile, etc., and one or more of these may be used.

In addition, the solubility coefficient of the above monomer is determined by Encyclopedi
a of Poly+*erSciences and
Technology(Wiley-1nLer-5c
This is based on the description published by Ience Co., Ltd.). In addition, the solubility coefficient of the multicomponent polymer was calculated assuming additive formation.

The modified vinyl ester/ethylene copolymer of the present invention can be obtained by adding the monomers and a radical initiator to the vinyl ester/ethylene copolymer latex and performing a kind of graft polymerization. Synthesized by means of □. After adding a dispersant for suspension polymerization to the vinyl ester/ethylene copolymer latex, such as an organic dispersant such as polyvinyl alcohol, polyvinylpyrrolidone, or methyl cellulose; an inorganic dispersant such as calcium phosphate, calcium carbonate, or magnesium oxide, the vinyl monomer Furthermore, in order to obtain a half-life of 10 hours, a monovalent radical initiator having a decomposition temperature of 50 to 130°C is added in an amount of 1 to 5 parts by weight per part of vinyl monomer. This is done by

In addition, a chain transfer agent such as dodecyl mercaptan or carbon tetrachloride may be used in combination to adjust the degree of polymerization.
(Such radical initiators include benzoyl peroxide, azobisisobutyronitrile,
t-Butyl peroxybenzoate, t-butyl peroxy (2-ethylhexanoate), di-isopropyl peroxy carbonate, t-butyl peroxy pivalate, t-butyl peroxy isopropyl carbonate, [-butyl lauryl peroxy] Examples include oxide.

Phase inversion from an emulsion system to a suspension system is carried out by adding vinyl monomer, but the phase inversion may also be carried out as the polymerization progresses, or it may be carried out by using a small amount of a highly scratchy organic solvent or inorganic salt. good,
The graft polymerization temperature is generally 60 to 130°C. The produced modified vinyl ester/ethylene copolymer is separated by simply stopping stirring, thoroughly washed with water, etc., and then dried. At this time, an anti-blocking agent may be used. For example, wax, polyethylene powder, silicone, etc. Organic and inorganic compounds include oil, silica, calcium carbonate, magnesium oxide, fatty acid salts such as calcium stearate, etc. Furthermore, additives such as antioxidants and ultraviolet absorbers may be added as necessary.

Since the modified vinyl ester/ethylene copolymer used in the present invention is usually grafted with a vinyl monomer, it has characteristics that cannot be seen in a simple blend of a vinyl ester/ethylene copolymer and a vinyl monomer polymer. can be seen.

〔Effect of the invention〕

The modified vinyl ester/ethylene copolymer produced by the production method of the present invention is obtained by changing the phase from an emulsion system at the start of the reaction to a suspension system at the end, and therefore the shape is usually 0.5mm in particle size. 1~
It has a 3fi bead shape and is easy to deposit, wash, dehydrate and dry the polymer. The dried modified vinyl ester/ethylene copolymer had lower ash content, lower water absorption, and less stickiness during storage than those produced by conventional emulsion polymerization. The PVC&I composition containing the modified vinyl ester/ethylene copolymer has the mechanical strength, filler filling properties, plasticizer non-migration properties, etc. that conventional emulsion-polymerized vinyl ester/ethylene copolymers had. In addition, the water resistance, electrical insulation properties, and non-adhesive properties of the sheet are improved.

Taking advantage of these properties, it can be used in a wide range of applications such as rubber parts, semi-conductive layers in power cables, and blended with PVC, etc., such as poultry hoses, flexible containers, leather, canvas, wire covering materials, and waterproof sheets. be able to.

〔Example〕

Hereinafter, the present invention will be specifically explained with reference to Examples. Note that all parts and % are parts by weight and % by weight.

Example 1 Sodium lauryl sulfate 1.5%, methylcellulose 0.3
4 parts of calcium phosphate and distilled water were added to 200 parts of latex of vinyl acetate/ethylene copolymer (ethylene content: 41%) obtained by polymerization in an emulsion system containing To this was added 50 parts of methyl methacrylate (solubility coefficient 9.4) in which 1.0 part of hensyl peroxide was dissolved at room temperature, and the mixture was kept under stirring for 1 hour to allow the vinyl monomer to be absorbed into the latex particles. . Subsequently, the temperature was raised to 75°C and reacted for 4 hours.
The temperature was further raised to 90°C and maintained for 2 hours.

When the temperature was lowered and stirring was stopped, the particle size was 0.2-0.
A bead-like precipitate of 5 cranes was obtained, which was washed with water and dried to obtain 238 parts of a modified vinyl acetate/ethylene copolymer. The analytical values and evaluation results of this polymer are shown in 2!1.

Example 2 Example 1 except that 50 parts of methyl methacrylate was replaced with 30 parts of ethyl acrylate (solubility coefficient: 9.2) in which 0.8 parts of benzoyl peroxide was dissolved and 10 parts of acrylonitrile (solubility coefficient: 15.5). A bead-like precipitate having a particle size of 0.1 to 0.3 mm was obtained in the same manner as in Example 1, and then washed with water and dried to obtain 225 parts of a modified vinyl acetate/ethylene copolymer. Table 1 shows the analytical values and evaluation results of this polymer.

Example 3 In Example 1, vinyl acetate/ethylene copolymer (ethylene content 22%) was used instead of vinyl acetate/ethylene copolymer, and methyl acrylate (solubility coefficient 9.7) was used instead of methyl methacrylate. )
241 parts of a modified vinyl versatate/ethylene copolymer was obtained in the same manner as in Example 1 except that .

Table 1 shows the analytical values and evaluation results of this polymer.

Comparative Example 1 Vinyl acetate/ethylene copolymer latex 2 of Example 1
Calcium chloride 20 parts (solid content) kept at 70°C
% aqueous solution little by little to coagulate and separate the polymer.

The obtained polymer was washed with water and dried to obtain 195 parts of vinyl acetate/ethylene copolymer. Table 1 shows the analytical values and evaluation results of this polymer.

Comparative Example 2 Vinyl acetate/ethylene copolymer latex 2 of Example 1
Added 50 parts of methyl methacrylate emulsified with 75 parts of an aqueous solution containing 1.9 parts of sodium lauryl sulfate and 0.4 parts of methyl cellulose to 0.00 parts (solid content), further added 0.15 parts of sodium bisulfite, and heated to 75°C. The temperature was raised, and 30 parts of a 5% aqueous solution of potassium persulfate was added dropwise over 4 hours. The obtained modified vinyl acetate/ethylene copolymer latex was coagulated, washed with water, and dried in the same manner as in Comparative Example 1. 215 parts of a modified vinyl acetate/ethylene copolymer was obtained. Table 1 shows the analytical values and evaluation results of this polymer.

Comparative Example 3 160 parts of vinyl acetate, 800 parts of distilled water, 1.6 parts of azobisisobutyronitrile (radical initiator), 1.6 parts of polyvinyl alcohol (dispersant), and After adding 0.8 parts of sodium polyacrylate (dispersant) and replacing the air in the autoclave with nitrogen and ethylene, the internal temperature was raised to 65°C, and ethylene was pressurized to 75 kg/cd for 8 hours. Suspension polymerization was performed. When the temperature was lowered and stirring was stopped, bead-like precipitates with a particle size of 0.5 to 1 fl were obtained, which were washed with water and dried to obtain 165 parts of vinyl acetate/ethylene copolymer. Analysis revealed that the ethylene content was 35%.
The Mooney viscosity was 3. Table 1 shows the evaluation results of this polymer.

Comparative Example 4 Polymerization was carried out in the same manner as in Example 1, except that 50 parts of butyl methacrylate (solubility coefficient: 8.3) was used instead of methyl methacrylate. Since phase inversion from an emulsion system to a suspension system was not sufficiently performed, the polymer was agglomerated, washed with water, and dried in the same manner as in Comparative Example 1. 221 parts of a modified vinyl acetate/ethylene copolymer was obtained. Table 1 shows the analytical values and evaluation results of this polymer.

The analysis and evaluation in the examples were carried out by the following methods.

◇ Ash Separation Approximately 10 g of the dried polymer was accurately weighed and collected in a porcelain crucible, burned in an electric furnace at 500°C for 1 hour, the weight was measured, and the ash content was calculated from the residual amount. It can be said that the lower the ash content, the lower the residual amount of coagulants, emulsifiers, etc.

Mooney viscosity measurement specimen (JIS K-6
300) was collected and immersed in tap water at 23°C for 7 days, and the water absorption rate was calculated from the weight change. The lower the water absorption rate, the better the properties such as water resistance and electrical insulation.

◇Grafting rate Carbon tetrachloride, which dissolves only the trunk poly(7-), was used as a solvent, and the insoluble portion was determined using a Soxhlet extractor, and the grafting rate was calculated from the increase in the insoluble portion. However, it was assumed that the dissolved content was only the vinyl ester/ethylene copolymer, and that all the grafted vinyl ester/ethylene copolymer was insoluble.

0 PVC blend physical properties A mixture of PVC SO part with an average degree of polymerization of 700, 2 parts of Ca-Zn composite stabilizer, 5 parts of epoxidized soybean oil, and 40 parts of the modified vinyl ester/ethylene copolymer of Example was prepared. 1 at a roll temperature of 170℃ using two wood kneading rolls.
The mixture was kneaded for 0 minutes. The kneaded product was press-molded at a press temperature of 175° C. for 5 minutes to obtain a sheet with a thickness of 1 ms. Using this sheet, the physical properties are evaluated in the following manner.

■Take a 5 x 5-sized sample from the water-resistant sheet and soak it in water at 50℃ for 1 hour.
The water absorption rate was measured from the change in weight after immersion for 20 hours. If the water absorption rate is 2% or less, it can be used in drinking tanks, etc. without any problems.

■ Electrical insulation Using the same sheets, the volume resistivity was measured according to JTS K-6723. Specific resistance is 3.5×10”Ω・1
If it is above, it passes without any problem even if it is used as a green liquor covering material.

(a) Mechanical properties Using the same sheet, mechanical properties were measured according to JIS K-6723. Tensile strength 120kt/- or more, elongation 2
If it is 50% or more, it can be used as a wire covering material without any problem.

■Transparency Using the same sheets, the light transmittance was measured according to JIS K-6723. If the i3 superweight is 0% or more, it can be passed as a packaging film without any problems.

■Take a strip of 2clI from the adhesive sheet, stick the two pieces together, apply a load of 1 pupil/-, and place in a dryer at 40°C for 24 hours.
I left it for a while. Thereafter, after being left at 23° C. for 2 hours, a 180° separation test was conducted using a tensile testing machine at a tensile rate of 20 B/min.

If the peel strength is 100 g/2 cm width or less, it can be used in flexible containers and the like without any problem.

Claims (1)

[Claims] Vinyl ester and ethylene in a weight ratio of 4:6 to 9:1
A vinyl monomer having a solubility coefficient of 85 or more is added to a vinyl ester/ethylene copolymer latex obtained by an emulsion polymerization method, and then polymerized under graft polymerization conditions and polymerized in a suspension system. A method for producing a modified vinyl ester/ethylene copolymer, characterized by completing the following steps.