JPH06228214A - Production of vinyl resin - Google Patents

Abstract

PURPOSE:To provide a vinyl resin excellent in antistatic properties, free from reduction of bulk density, exhibiting an excellent fluidity and capable of forming an almost colorless and transparent film regardless of the kind of a dispersion stabilizer used in polymerization. CONSTITUTION:This method for production of a vinyl resin comprises polymerizing a vinyl monomer such as vinyl chloride in an aqueous medium and adding an A-B type block copolymer containing a block component composed of a polyvinyl alcohol-based polymer as the (A) component and another block component composed of a lipophilic polymer such as polymethyl methacrylate as the (B) component thereto in an amount of 0.005 to 5.0 pts.wt. based on 100 pts.wt. vinyl monomer at a point of time when the conversion exceeds 60%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a vinyl resin, and more particularly to a method for producing a vinyl resin which has excellent fluidity and is suitable as a molding material for a colorless transparent film.

[0002]

2. Description of the Related Art Vinyl chloride resin, which is one of the typical examples of vinyl resin, is a dispersion stabilizer containing vinyl chloride monomer or a mixture of vinyl monomers containing vinyl chloride monomer as a main component. It is obtained by polymerizing in an aqueous medium containing a polymerization initiator and the like. However, the polymer powder thus obtained has a problem that it tends to be charged with static electricity during drying or transportation, its fluidity is lowered to form a block, and a transportation pipe or the like is clogged. Also, the charged polymer powder is
There is a problem that the bulk density (bulk specific gravity) is significantly reduced. It should be noted that these phenomena are likely to occur especially in winter when the humidity is low. By the way, vinyl chloride resin is
Molded as films, pipes, containers, etc. When a vinyl chloride resin is used as a film, it has excellent transparency, but when several sheets of this film are stacked, there is a problem that the color tone differs depending on the type of dispersion stabilizer used for polymerization. Conventionally, for the purpose of preventing electrification of vinyl chloride resin, a method of improving water retention on the resin surface by adding a nonionic, cationic or anionic surfactant is known, but the effect is insufficient. Not only that, but there was a fatal drawback that the thermal stability was impaired.

Another known method is to add a small amount of polymethylmethacrylate having a particle diameter of 0.5 μm or less after the polymerization rate of vinyl chloride reaches 70%. However, although this method improves the fluidity, it has not solved the problem that the color tone of the film varies depending on the type of dispersion stabilizer used. Furthermore, the research group of the inventors of the present invention is a dispersion for suspension polymerization of vinyl chloride composed of a block copolymer composed of a polyvinyl alcohol-based polymer and a lipophilic polymer, and polyvinyl alcohol having a specific saponification degree and a polymerization degree. Stabilizers are disclosed in JP-A-64-75505 and JP-A-3-290402. In these inventions, the dispersion stabilizer consisting of the above two components is added to the reaction system before the initiation of the polymerization, and the effect of improving the particle size distribution, porosity, bulk specific gravity, thermal stability, processing characteristics, etc. of vinyl chloride is obtained. However, the effect of improving the flow characteristics and the color tone of the film was not recognized.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks of the prior art, to prevent electrostatic charge, to reduce the bulk specific gravity, to have good fluidity, and to have a good color tone during film formation due to polymerization. It is to develop a method capable of obtaining a vinyl resin that is almost colorless and transparent regardless of the type of dispersion stabilizer used.

[0005]

Means for Solving the Problems The present inventors have made extensive studies in order to achieve the above object. As a result, when a vinyl-based monomer such as vinyl chloride is polymerized in an aqueous medium, the polymerization is performed using polyvinyl alcohol as a dispersion stabilizer until the polymerization rate reaches 60%.
It has been found that the above object can be achieved by adding an AB type block copolymer to the reaction system after exceeding the above range. The present invention has been completed based on such findings.

That is, according to the present invention, a vinyl-based monomer is polymerized in an aqueous medium and, after the polymerization rate exceeds 60%, 100 parts by weight of the vinyl-based monomer is added to formula AB. Block copolymer 0.005 represented by (I) (wherein A is a block component made of a polyvinyl alcohol-based polymer and B is a block component made of a lipophilic polymer)
The present invention provides a method for producing a vinyl-based resin, which comprises adding 5.0 parts by weight to a polymerization system.

First, the block copolymer represented by the formula (I) used in the present invention (hereinafter referred to as an AB block copolymer) will be described. The A-B type block copolymer usually means that the A component and the B component are linearly bonded to each other to form a main chain, but both the A component and the B component, Alternatively, it also includes a graft copolymer in which either one is grafted to the main chain. Further, this block copolymer is not limited to one in which the A component and the B component are directly bonded, but is also in the form of being bonded via a sulfur atom, for example, the formula A-S-B (S represents sulfur). Also includes things. Here, the component A is a block component made of a polyvinyl alcohol polymer. The polyvinyl alcohol-based polymer is generally obtained by hydrolyzing a polyvinyl ester-based polymer, but the vinyl ester-based monomer is not particularly limited,
For example, one or more of various vinyl esters such as vinyl formate, vinyl acetate, vinyl propionate, and vinyl pivalate are used. Of these, vinyl acetate and vinyl pivalate are industrially preferable. As the polyvinyl alcohol-based polymer (hereinafter sometimes abbreviated as PVA), those having various degrees of polymerization and saponification can be used, but the degree of polymerization is usually 50 to 50.
Those having a saponification degree of 3000 or more and 50 mol% or more are used. Further, the component A may be obtained by copolymerizing a monomer containing an ionic group, a nonionic group and the like in a small proportion of 10 mol% or less.

On the other hand, the component B is a block component composed of a lipophilic polymer. Here, the lipophilic property means that a portion other than PVA, which is one component of the block copolymer, has a property of dissolving in a solvent other than water in the case of a homopolymer. As the lipophilic polymer, various ones can be used, provided that they are different from the constitutional unit of the above-mentioned component A. For example, acrylic acid esters, methacrylic acid esters,
Examples thereof include those comprising constitutional units derived from at least one selected from vinyl esters, α-olefins and vinyl chloride. As the acrylic acid ester and methacrylic acid ester (hereinafter, acrylic acid and methacrylic acid may be collectively referred to as (meth) acrylic acid), an alkyl group having 1 to 22 carbon atoms or a cycloalkyl group is usually used. Further, esters having an arylalkyl group are preferable, and specific examples thereof include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, and (meth) acrylic. Cyclohexyl acid, tert-butyl cyclohexyl (meth) acrylate, amyl (meth) acrylate, octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, decyl (meth) acrylate, lauryl (meth) acrylate, Cetyl (meth) acrylate, (meth)
Stearyl acrylate, behenyl (meth) acrylate,
Examples thereof include benzyl (meth) acrylate. Also,
Examples of vinyl esters include vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl versaticate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate,
Examples include vinyl palmitate, vinyl stearate, vinyl oleate, and vinyl pivalate. When the vinyl ester is saponified and used, the saponification degree is preferably adjusted to 50 mol% or less. Also,
Examples of α-olefins include ethylene, propylene and styrene. Of these, (meth) acrylic acid esters, vinyl esters, and polymers or copolymers containing vinyl ester and ethylene as constituent monomers are preferably used.

The method for producing the block copolymer used in the present invention is not particularly limited, and various methods can be adopted. However, a method of radically polymerizing an oil-soluble monomer that constitutes the component B in water in the presence of a polyvinyl alcohol-based polymer (component A) having a thiol group at one end, or an oil having a thiol group at the end A method in which, in the presence of a soluble polymer (component B), radical polymerization is carried out in a common solvent of this polymer and vinyl esters, which are monomers constituting the component A, and the resulting block copolymer is saponified. Is preferred. In this case, the component A and the component B are block copolymers (formula A-S
-B) is obtained. Of the above methods, the former method is more preferable. Incidentally, such a manufacturing method is described in detail in JP-A-59-189111. The weight ratio of the A component and the B component in the AB block copolymer used in the present invention is not particularly limited, but is preferably 1/4 to 4/1, more preferably 1/3 to 2/1.
It is preferable to be selected from the range. If it is out of this range, the desired effect may be insufficient in some cases. Further, there is no particular limitation on the form in which the AB block copolymer is added to the polymerization system of the vinyl-based monomer, and it may be added as a solid such as powder, or as an aqueous dispersion. Although it may be added, the latter method is industrially preferable. When used as an aqueous dispersion, the particle size of the AB block copolymer is preferably 1 μm or less, more preferably 0.5 μm or less, still more preferably 0.2 μm or less.

The AB type block copolymer as described above is a vinyl-based block copolymer when the polymerization rate of the vinyl monomer exceeds 60%, and preferably when the polymerization rate reaches 70 to 85%. The AB block copolymer is added to the polymerization system in an amount of 0.005 to 5.0 parts by weight, preferably 0.05 to 0.20 parts by weight, based on 100 parts by weight of the monomer. If the amount of the AB block copolymer is less than 0.005 polymerized portion, the desired effect cannot be obtained, and if it exceeds 5.0 polymerized portion, scale adhesion during polymerization increases.

To carry out the method of the present invention, when a vinyl monomer is polymerized in an aqueous medium, a conventional dispersion stabilizer or dispersion aid is used at the start of the polymerization. Examples of the dispersion stabilizer or dispersion aid used at this time include:
Water-soluble PVA having a saponification degree of 65 to 98 mol% and a polymerization degree of 300 to 4000, a saponification degree of less than 65 mol% and a polymerization degree of 100
A water-soluble PVA of up to 2000, a degree of saponification of 50 mol% or less, and a self-emulsifying PVA having an ionic group in the main chain or at the terminal are preferable. Also, a high degree of polymerization PVA having a degree of polymerization of 4000 or more can be used. Generally, these dispersion stabilizers or dispersion aids are used alone or in combination of two or more. The amount of the vinyl monomer 10
0.005 to 2 parts by weight is preferable with respect to 0 polymerization part, and 0.0
It is more preferably 1 to 0.5 parts by weight. In addition, methyl cellulose, ethyl cellulose, hydroxyethyl cellulose,
Water-soluble cellulose esters such as hydroxypropyl cellulose and hydroxypropyl methyl cellulose, acrylic acid polymers, water-soluble polymers such as gelatin, sorbitan monolaurate, sorbitan trioleate, sorbitan monostearate, glycerin tristearate, ethylene oxide propylene oxide An oil-soluble emulsifier such as a block copolymer, a water-soluble emulsifier such as polyoxyethylene sorbitan monolaurate, polyoxyethylene glycerin oleate, sodium laurate and the like are added as necessary in one kind or in a combination of two or more kinds. The amount added is not particularly limited, but is preferably 0.05 to 2 parts by weight, and more preferably 0.01 to 0.5 parts by weight, per 100 parts by weight of vinyl-based monomer such as vinyl chloride.

A polymerization initiator may be used in the polymerization of vinyl monomers, and the polymerization initiator may be any of those conventionally used in the polymerization of vinyl monomers such as vinyl chloride. Is di-2-ethylhexyl peroxydicarbonate, diisopropyl peroxydicarbonate,
Percarbonate compounds such as diethoxyethyl peroxydicarbonate, t-butyl peroxy nepivalate, t-hexyl peroxy pivalate, α-cumyl peroxyneodecanate, 2,4,4-trimethylpentyl-2- Perester compounds such as peroxy-2-neodecanate, acetylcyclohexylsulfonyl peroxide, 2,4,4-trimethylpentyl-2-peroxyphenoxyacetate, 3,5,5-trimethylhexanoyl peroxide, lauroyl peroxide, etc. Examples thereof include peroxides, azo compounds such as 2,2′-azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, and azobis (4-methoxy-2,4-dimethylvaleronitrile). Is potassium persulfate, ammonium persulfate , Hydrogen peroxide, etc. cumene hydroperoxide can also be used, can also be used in one or two or more combinations of those above various. This addition amount is preferably in the range of 0.02 to 0.3 parts by weight per 100 parts by weight of vinyl-based monomer such as vinyl chloride.

After the polymerization rate of the vinyl monomer exceeds 60%, the proportion of the AB block copolymer 0.005-5.0 parts by weight relative to 100 parts by weight of the vinyl monomer. If it is added to the polymerization system at the time of polymerization, at the time of polymerization, an aqueous medium, a vinyl-based monomer, a dispersion aid or a dispersion stabilizer, a polymerization initiator, a charging method, a charging ratio, a charging water, etc. Various polymerization conditions such as temperature and polymerization temperature may be set in the same manner as in the conventional case. In addition, various additives usually used in the production of vinyl polymers, such as polymerization regulators, chain transfer agents, pH regulators, gelation improvers, antistatic agents, crosslinking agents,
Stabilizers, fillers, buffers, scale inhibitors and the like can be added as required. Further, an antioxidant may be added to the polymerization system before the initiation of the polymerization, during the polymerization or after the completion of the polymerization for the purpose of suppressing the polymerization reaction and preventing the deterioration of the produced polymer. Furthermore, the polymerization rate of vinyl monomer is 60.
%, And when the AB block copolymer is added,
JP-A-64-75505 and JP-A-3-29040
As disclosed in Japanese Patent Publication No. 2 and the like, a PVA-based dispersion aid can also be used in combination.

There are various kinds of vinyl monomers which are raw materials of the vinyl resin produced in the present invention. Specifically, vinyl chloride alone and a monomer mixture mainly containing vinyl chloride ( Vinyl chloride (50% by weight or more) is included, and as the comonomer copolymerized with vinyl chloride, vinyl esters such as vinyl acetate and vinyl propionate, methyl (meth) acrylate, ethyl (meth) acrylate and the like ( (Meth) acrylic acid ester, olefins such as ethylene and propylene, vinyl ethers such as lauryl vinyl ether and isobutyl vinyl ether, maleic anhydride, acrylonitrile, itaconic acid, styrene, vinylidene chloride, and other monomers copolymerizable with vinyl chloride are exemplified. These can be used alone or in combination of two or more. Further, the above vinyl-based monomers containing no vinyl chloride can be used alone or in combination of two or more.

If necessary, various rubber components may be added to the vinyl chloride resin such as the vinyl chloride resin obtained by the suspension polymerization method of the present invention. Examples of the rubber component that can be added here include polybutadiene, styrene-butadiene block polymer, nitrile rubber, maleated rubber, polyisoprene rubber, butadiene-acrylonitrile rubber, ethylene-propylene-diene terpolymer, butadiene-styrene-butadiene. Examples thereof include terpolymers and butadiene-isoprene-butadiene terpolymers. Similarly, metal soaps such as calcium stearate, zinc stearate, barium stearate, cadmium stearate and lead stearate, which have been conventionally used as stabilizers for vinyl chloride resins, dibasic sulfates, dibasic stearin. Lead acid,
Inorganic stabilizers such as calcium hydroxide and calcium silicate,
Furthermore, lubricants, pigments, fillers, impact modifiers, processing aids, UV absorbers, etc. may be added later.

[0016]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the following examples, "%" and "parts" mean "% by weight" and "parts by weight" unless otherwise specified. Example 1 (1) Production of Block Copolymer A polymerization vessel having a thiol group at one end has a polymerization degree of 750.
And 80 parts of PVA with a saponification degree of 91.8 mol% and water 980
Part, and after heating, pVA of PVA aqueous solution with 1N sulfuric acid
The H was adjusted to 3. Next, after adding 40 parts of methyl methacrylate and thoroughly stirring and mixing, nitrogen substitution was carried out to 70
The temperature was raised to ° C. 100 parts of a 0.5% aqueous solution of potassium perbromate was continuously added to this system over 90 minutes with stirring, and polymerization was further performed at 70 ° C. for 90 minutes. The obtained block copolymer was an emulsion in which the weight ratio of the PVA part to the polymethylmethacrylate part was 2/1, the solid content concentration was 9.8%, and the average particle size was 0.10 μm. This block copolymer emulsion was formed into a film having a thickness of 0.1 mm by a casting method and extracted with water which is a solvent of PVA and acetone which is a solvent of polymethylmethacrylate to remove respective homopolymers. It was found that the block copolymer insoluble in both solvents was 95%.

(2) Manufacture of vinyl resin A polymerization vessel made of stainless steel having an internal volume of 100 liters was charged with 50 kg of deionized water and the dispersion stabilizer shown in Table 1 and the inside of the vessel was deaerated. A body of 35 kg was introduced. 14 g of di-2-ethylhexyl peroxydicarbonate as a polymerization initiator while stirring the inside of the container
Then, the temperature was started to start the polymerization, and when the temperature in the polymerization vessel reached 57 ° C., stirring was continued while maintaining the temperature, and when the polymerization rate reached 70 to 85%, vinyl chloride 100 The AB block copolymer shown in Table 1 was added to parts by weight, and the polymerization was further continued. When the internal pressure of the polymerization vessel reached 5.5 kg / cm ² G, the polymerization reaction was stopped, unreacted monomers were released, and dehydration drying was carried out to obtain a vinyl chloride polymer powder. Table 1 shows the types and amounts of the dispersant (dispersion stabilizer) and AB block copolymer used in the polymerization, and Table 2 shows the performance of the obtained vinyl chloride resin.

Examples 2 to 12 and Comparative Examples 1 to 3 Examples except that the type and amount of the dispersant (dispersion stabilizer) and the AB block copolymer were changed as shown in Table 1. Suspension polymerization of vinyl chloride was carried out in the same manner as in 1.
The performance of the obtained vinyl chloride resin is shown in Table 2.

[0019]

[Table 1]

[0020]

[Table 2]

In Table 1, symbols indicate the following. PMMA: Polymethylmethacrylate PVAc: Polyvinylacetate PSt: Polystyrene PMMA / PBA: Polymethylmethacrylate / n-butyl polyacrylate EVA: Poly (ethylene-vinyl acetate)

[0022]

[Table 3]

[0023]

[Table 4]

The measurement of the average particle diameter and various tests shown in Table 2 are carried out by the following method. The average particle diameter was measured by dry sieving analysis using a wire mesh based on Tyler mesh. Flowability test Each of the obtained vinyl chloride polymer powders was allowed to stand in an environment of 20 ° C and a relative humidity of 40% for 3 days, and then JIS K-6 was used.
100g was put into the bulk density measuring funnel of No. 721, and the fall time from the funnel was measured. Similarly, each vinyl chloride polymer powder that was left for 3 days was mixed with a Brabender planetary mixer at 60 rpm for 5 minutes and charged, and then the dropping time from the funnel was measured by the same method as above. .

Bulk Specific Gravity Measurement Test Each polymer powder was placed in an environment of 20 ° C. and 40% relative humidity for 3 days.
After standing for a day, the measurement was performed according to JIS K-6721. Similarly, each vinyl chloride polymer powder that had been left for 3 days was mixed with a Brabender planetary mixer at 60 rpm for 5 minutes and charged, and then the bulk specific gravity was measured in the same manner as above. Color tone of film 100 parts of each polymer powder, 2.5 parts of dibutyltin maleate and 80 parts of dioctyl phthalate were mixed and kneaded on a roll at 160 ° C. for 10 minutes to prepare a sheet having a thickness of 0.8 mm. This was cut out into a square sheet having a side of 30 cm, 20 sheets of this sheet were overlapped, and the color tone was judged under natural light.

[0026]

As is apparent from the above description, the vinyl resin obtained by the method of the present invention has a large particle size, so that it is less likely to be scattered during handling, and is less likely to be charged, resulting in a decrease in bulk specific gravity. In addition, it has excellent fluidity, no scale is attached, and the color tone during film formation is almost colorless and transparent irrespective of the type of dispersion stabilizer used for polymerization.

Claims (1)

[Claims] 1. A vinyl monomer is polymerized in an aqueous medium,
After the polymerization rate exceeds 60%, the vinyl monomer 100 is added.
Based on parts by weight, a block copolymer represented by the formula: AB (wherein A is a block component composed of a polyvinyl alcohol-based polymer and B is a block component composed of a lipophilic polymer). 0.005-
A method for producing a vinyl-based resin, which comprises adding 5.0 parts by weight to a polymerization system.