JPH04285610A - Production of vinylidene chloride resin particle - Google Patents

Abstract

PURPOSE:To easily produce partially crosslinked spherical amorphous vinylidene chloride resin particles having relatively large particle diameter and controlled particle size distribution. CONSTITUTION:A partially crosslinked amorphous vinylidene chloride resin particle is used as a seed particle. The seed particle is swollen with a copolymerizable unsaturated monomer composed mainly of vinylidene chloride in an amount less than critical swelling degree in the presence of a polyvinyl alcohol having low polymerization degree and is suspension-polymerized in water in the presence of a suspension stabilizer.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention has a relatively large particle size,
Furthermore, the present invention provides a method for easily producing amorphous vinylidene chloride resin particles having a spherical shape at a high yield, and a method for controlling the particle size distribution. The amorphous vinylidene chloride resin particles obtained by the present invention are particularly useful as raw material particles for producing excellent vinylidene chloride resin molded articles by bead foaming.

0002

[Prior Art] A foamed molded product made of vinylidene chloride resin particles with excellent heat insulation properties and heat resistance by a bead foaming method is described in JP-A-63-170434, in which partially crosslinked amorphous vinylidene chloride resin particles are used. The manufacturing method is disclosed in JP-A-63-1
No. 2713. Partially crosslinked amorphous vinylidene chloride resin particles used in the bead foaming method are difficult to manufacture by once melting and extrusion granulation, so they are directly manufactured by suspension polymerization. Although the particle size distribution depends on the application, it is generally preferable to have a narrower particle size distribution. This is because if the particle size distribution is wide, the amount of blowing agent impregnated into the resin will be distributed from particle to particle, resulting in deterioration of the physical properties of the foam molded product or problems with the appearance of the molded product.

[0003] In the usual suspension polymerization method, it is difficult to avoid the existence of a flow energy distribution at each position in a stirring tank and the occurrence of a statistical probability distribution in the collision of droplets, and therefore the resultant resin particles It has the disadvantage that the particle size distribution becomes wider. In the field of manufacturing technology for styrene resins, vinyl chloride resins, methyl methacrylic resins, crystalline vinylidene chloride resins, etc., it is known to manufacture these resins by suspension polymerization. In particular, in the field of styrenic resins, where foam moldings are frequently produced by bead foaming, styrenic resin particles with a desired center diameter and narrow particle size distribution are produced by suspension polymerization in a high yield. Many methods of production have been proposed.

[0004] These are methods characterized by suspension agents as described in Japanese Patent Publications No. 45-39459 and Japanese Patent Publication No. 46-21449, etc., and methods characterized by suspension agents as described in Japanese Patent Publication No. 57-10610 etc. A method characterized by proceeding to suspension polymerization after bulk polymerization, Japanese Patent Publication No. 40-824, Japanese Patent Publication No. 1987-57-
As described in No. 70111, etc., the method can be broadly classified into methods characterized by dissolving a styrene monomer in a styrenic resin and then subjecting it to suspension polymerization. However, in all of these methods, it is difficult to avoid the occurrence of distribution in the dispersion and coalescence of droplets, and the resulting resin particles have a wide particle size distribution, which is not satisfactory. Special Publication No. 46-2987, Special Publication No. 49-191
The method described in No. 11 etc. is an improved method of these, in which uncrosslinked styrene resin particles of uniform particle size are dispersed in water, and styrene is mainly used in an amount that causes the resin particles to swell but not dissolve. It was proposed as a method characterized by suspension polymerization by supplying monomers intermittently or continuously. However, in this method, it is necessary to maintain the monomer in the polymerization system at a weight ratio of monomer + polymer of about 0.6 or less. This method requires intermittent or continuous addition of stabilizers, etc., is complicated in terms of management and equipment, and is not necessarily a satisfactory method.

[0005] The present inventors have already developed a method for producing amorphous vinylidene chloride resin particles as described in Japanese Patent Application Laid-Open No. 2-153.
No. 911 proposes a method for controlling particle size distribution. In this method, partially crosslinked amorphous vinylidene chloride resin particles are heated at room temperature to around the polymerization temperature by 1% of the weight of the resin.
It was discovered that it swells with a copolymerizable unsaturated monomer mainly composed of vinylidene chloride in an amount up to 20 times the amount, and this is an epoch-making product that utilizes this fact. However, when the scale of polymerization increases, it may not be possible to reproducibly disperse the swollen particles into individual particles after adding the suspension stabilizer. Furthermore, it is difficult to set conditions for individual dispersion.

[0006]

[Problems to be Solved by the Invention] The problem to be solved by the present inventors is that in the production of amorphous vinylidene chloride resin particles, the particle size is relatively large and the shape is spherical.
The object of the present invention is to provide a method for stably producing particles with a controlled particle size distribution and a small amount of aggregates at a high yield, independent of scale.

[0007]

[Means for Solving the Problems] As a result of intensive research to solve the above problems, the present inventors have developed a method for producing copolymerizable unsaturated monomers mainly composed of vinylidene chloride, using amorphous vinylidene chloride resin particles. We discovered that stable beads with less aggregation can be obtained by swelling them with a polymer, a crosslinking agent, and a polymerization initiator and then carrying out aqueous suspension polymerization.Based on these findings, we completed the present invention. .

That is, the present invention uses amorphous vinylidene chloride resin particles as seed particles, and copolymerizable unsaturated monomers mainly consisting of vinylidene chloride in an amount such that the degree of swelling is equal to or less than the limit swelling degree of the seed particles. Amorphous vinylidene chloride, which is characterized in that the seed particles are swollen with a polyvinyl alcohol, a crosslinking agent, and a polymerization initiator in the presence of low polymerization degree polyvinyl alcohol, and subjected to aqueous suspension polymerization in the presence of a suspension stabilizer. This is a method for producing resin particles.

In the present invention, the amorphous vinylidene chloride resin particles (hereinafter simply referred to as seed particles) used as seed particles contain vinylidene chloride, one or more copolymerizable unsaturated monomers, and one kind of copolymerizable unsaturated monomer. Contains a compound (hereinafter referred to as a crosslinking agent) having two or more of the above copolymerizable double bonds in the molecule. A preferred method for producing such seed particles includes 30 to 85 parts of vinylidene chloride and 15 to 15 parts of one or more copolymerizable unsaturated monomers.
Examples include a method of carrying out aqueous suspension polymerization of at least 70 parts and a crosslinking agent in the presence of a radical polymerization initiator and a suspension stabilizer.

Examples of copolymerizable unsaturated monomers include vinyl chloride, acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, vinyl acetate, acrylic acid, methacrylic acid, acrylic acid alkyl esters, and methacrylic acid alkyl esters. , glycidyl acrylate, N-substituted maleimide such as N-phenylmaleimide, N-hexylmaleimide, N-2chlorophenylmaleimide, and other known monomers.

[0011] As the crosslinking agent, diacrylic acid esters of diols such as divinylbenzene, ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, neopentyl glycol, dimethacrylic acid esters, trimethylol, etc. Known crosslinking agents such as propane triacrylate, trimethacrylate, and tetraallyloxy ester can be used.

[0012] By adjusting the amount of crosslinking agent, the gel fraction (described below) of the seed particles can be adjusted.
The amount of crosslinking agent can be determined so that the gel fraction of the seed particles has a desired value. Known radical polymerization initiators and suspension polymerization stabilizers can be used. The seed particles used in the present invention have a limit swelling degree (hereinafter referred to as LS) defined below.
(referred to as I) or less.

[0013] If the seed particles are crystalline, the LSI will be low, which is undesirable, so it is necessary that the seed particles be amorphous. Generally, a resin containing 85% by weight or less of structural units derived from vinylidene chloride is amorphous. Amorphous means that it does not show an endothermic peak due to crystal melting in differential thermal analysis (DSC), or does not show a clear analytical peak due to crystals in wide-angle X-ray analysis. If the gel fraction exceeds 85%, the LSI will be low and it will not be suitable for the purpose of the present invention, so it is preferably 85% or less.

[0014] The gel fraction refers to the ratio of 1 to 2 g of resin to 50
After immersing in twice the amount of tetrahydrofuran at 40°C for 1 hour with stirring, the soluble and insoluble components are separated by filtration, and the tetrahydrofuran is removed by evaporation, and the value is determined from the weight of the resulting tetrahydrofuran insoluble component using the following formula. . Gel fraction (%) = (weight of insoluble matter) x 100/(weight of resin before immersion) In addition, the limit swelling degree (LSI) is The value is determined by the following formula from the weight of the resin particles after being immersed at room temperature for 1 hour with stirring, filtered through a 200-mesh wire mesh, and the monomer remaining on the wire mesh is swollen.

Limiting degree of swelling (LSI) = (weight of resin particles with monomers swollen)/(weight of resin particles before immersion) Amount of monomer used in the production method of the present invention (hereinafter also referred to as seed polymerization) Radically polymerizable unsaturated monomers can be used as monomers, including mixed monomers containing 30 parts to 85 parts of vinylidene chloride and 15 parts to 70 parts of one or more copolymerizable unsaturated monomers. is preferred. In the present invention, the term "part" refers to the total weight of vinylidene chloride and one or more copolymerizable unsaturated monomers as 100.

If vinylidene chloride is less than 30 parts, the original properties of the resulting resin such as flame retardancy, gas barrier properties, and chemical resistance will deteriorate, and if it exceeds 85 parts, the resin will develop crystallinity and bead foaming may occur. The impregnability of the blowing agent decreases. As the copolymerizable unsaturated monomer and crosslinking agent used in the seed polymerization, the known ones mentioned in the explanation of the seed particles can be used.

As the radical polymerization initiator, known ones such as lauryl peroxide and benzoyl peroxide can be used. As the suspension stabilizer, known ones such as hydroxypropyl methyl cellulose and partially saponified polyvinyl alcohol (preferably those with a degree of polymerization of 1000 or more and a degree of saponification of 98 mol% or less, hereinafter abbreviated as PVA) can be used. .

The low polymerization degree polyvinyl alcohol added during seed polymerization must have a polymerization degree of 500 or less and a saponification degree of 95 mol % or less. The low polymerization degree polyvinyl alcohol is first adsorbed on the surface of the unsaturated monomer, and when it is absorbed by the seed particles, it is adsorbed on the surface of the swollen particles, and has the effect of mitigating aggregation between the swollen particles. When the degree of polymerization of the low polymerization degree polyvinyl alcohol exceeds 500, the unsaturated monomer tends to be stabilized as oil droplets in the aqueous phase, which prevents the seed particles from swelling and generates fine particles. A similar effect is obtained when the amount added is large. Furthermore, if the amount added is small, the effect of reducing aggregated particles will be reduced. Therefore, the amount of low polymerization degree polyvinyl alcohol added is preferably 0.5 part to 0.001 part, and more preferably 0.05 part to 0.001 part.
It is 0.005 part.

[0019] If low polymerization degree polyvinyl alcohol is not added, the swollen particles will be strongly fused to each other, so even if a suspension stabilizer is added, it will be difficult to disperse them as individual swollen particles. If the reaction continues as it is, several tens of percent of the particles will be generated as two or several aggregated particles. Furthermore, when polyvinyl alcohol with a low degree of polymerization is used, swelling can proceed stably even in areas where the gel fraction is low.

According to the seed polymerization of the present invention, the particle size distribution of the produced particles is determined by the particle size distribution of the seed particles and the degree of swelling (hereinafter referred to as SI), and is determined by the type and amount of suspension stabilizer and the strength of stirring. is virtually unaffected. In seed polymerization, SI is preferably less than LSI. This is because if it is less than LSI, substantially the entire amount of the swollen monomer will be polymerized within the seed particle. The average particle size can be approximately 1/3 (SI) times that of the seed particles. The particle size distribution can also be shifted in parallel by (SI) 1/3 times that of the seed particles. When the LSI is exceeded, monomers that do not swell are present in the seed particles, which become fine particles through polymerization, making it impossible to control both the average particle size and particle size distribution.

[0021] The degree of swelling (SI) is a value obtained from the following equation from the weight of seed particles (Ws) and the weight of monomer (Wm) used in the seed polymerization method. Swelling degree (SI) = (Ws+Wm)/Ws The swelling of the monomer, crosslinking agent, and radical polymerization initiator into the seed particles occurs in the presence of low polymerization degree polyvinyl alcohol at a temperature below the polymerization initiation temperature. This can be achieved by mixing and stirring water, a monomer, a crosslinking agent, and a radical polymerization initiator. Next, by stirring and adding a suspension stabilizer, the seed particles swollen with monomers and the like are individually dispersed. Thereafter, desired resin particles can be obtained by raising the temperature to a predetermined temperature and conducting a reaction.

As explained above, in other words, the present invention is a polymerization method in which the monomer that causes the seed particles to swell and expand is substantially polymerized within the seed particles, and the particle size of the seed particles and This is a polymerization method in which particle size distribution can be controlled by selecting SI. Therefore, this is a polymerization method that is completely different from conventional particle size control methods, such as the type and amount of suspending agent, the viscosity of the mixture of monomer and polymer, and the addition of a small amount of monomer. Furthermore, according to the method of the present invention, resin particles having a non-standard particle size can be changed to a particle size within the standard and used.

[0023]

[Examples] The present invention will be explained below with reference to Examples.
The invention is not limited to these examples. In addition, parts in Examples represent parts by weight. In addition, the particle size is displayed as follows. (Example) 0.1mm/0.2mm: 0.1mm or more, 0.
Less than 2mm

[0024]

[Examples 1 to 3] A solution prepared by dissolving PVA as a suspending agent in 100 parts of water was charged into a reaction vessel, and then 7 parts of N-phenylmaleimide, 20 parts of acrylonitrile, 23 parts of styrene, 1,6- Hexanediol diacrylate 0
．． A monomer mixture solution prepared by dissolving 0.07 parts of a mixed solution in advance and further mixing 50 parts of vinylidene chloride, and 0.8 parts of lauryl peroxide as a radical initiator were charged. After purging with nitrogen, stirring was started, the temperature was raised to 60°C, and the reaction was carried out for 26.5 hours. The resulting resin particles were separated by filtration, washed with water and dried. The residual monomer content in the obtained resin particles was all 0.5% or less, and the polymerization rate was 98% or more.

[0025] The particle size obtained by sieving is 0.1 to 0.
The gel fraction and limit swelling degree of 4 mm resin particles are as follows.
Content Gel fraction
Limit swelling degree 0.1mm~0.2mm:
11% 41%
11 0.2mm~0.3mm: 65%
43% 11
0.3mm~0.4mm: 24%
43% 11th, water 10
A low polymerization degree polyvinyl alcohol having a polymerization degree of 100 and a saponification degree of 50 to 70 mol% is dissolved in 0 parts by weight shown in Table 1, and 20 parts of resin particles having the above particle size of 0.1 to 0.4 mm are used as seed particles. into a reaction vessel, and further a monomer mixed solution in which 7 parts of N-phenylmaleimide was dissolved in 20 parts of acrylonitrile, 23 parts of styrene, 50 parts of vinylidene chloride, and 0.065 parts of 1,6-hexanediol diacrylate; After adding 0.8 parts of lauryl peroxide, the mixture was stirred for 1 hour. The degree of swelling was 6.

Next, an aqueous solution of 0.3 parts of PVA dissolved in 14 parts of water was added, and after stirring for 1 hour, the temperature was raised to 60°C. 26.
The reaction took place for 5 hours. The results are shown in Table 1. In Examples 1 to 3, the particle size produced was approximately the same as the theoretical value. Further, no aggregates were generated. The theoretical value here refers to the particle size of the seed particles represented by a heterogeneous weight distribution, which is expressed as (SI)
This is the value obtained by moving 1/3 times in parallel. In each case, there were no aggregates in the resin particles obtained, and particle size distributions that approximately matched the theoretical values were obtained.

[0027]

Example 4 Similar to Examples 1 to 3, resin particles having a particle size of 0.1 to 0.4 mm obtained by sieving were used as seed particles. Next, 20 parts of the above seed particles and low polymerization degree polyvinyl alcohol (polymerization degree 100) were added to 100 parts of water.
, degree of saponification 50 to 70 mol%), 0.01 part of Example 1
In addition, a monomer mixed solution in which 8 parts of N-phenylmaleimide was dissolved in 22 parts of acrylonitrile, 25 parts of styrene, 45 parts of vinylidene chloride, and 0.02 parts of divinylbenzene, and 0.0 parts of lauryl peroxide were prepared in the same manner as in 3. 8
After adding 1 part, the mixture was stirred for 1 hour. The degree of swelling was 6.

Next, 0.3 part of PVA was dissolved in 14 parts of water, and the mixture was stirred for 1 hour and then heated to 60°C.
．． The reaction took place for 5 hours. The results are shown in Table 2. The limit swelling degree is 1
2 was shown. There were no aggregates in the obtained resin particles,
The results were good.

[0029]

[Example 5] In the same manner as in Examples 1 to 3, resin particles having a particle diameter of 0.1 to 0.4 mm obtained by sieving were used as seed particles. Next, 20 parts of the above seed particles and low polymerization degree polyvinyl alcohol (polymerization degree 300) were added to 100 parts of water.
, degree of saponification 50-70 mol%) in Examples 1-
A monomer mixture solution containing 7 parts of N-phenylmaleimide, 20 parts of acrylonitrile, 23 parts of styrene, 50 parts of vinylidene chloride, 0.065 parts of 1,6-hexanediol diacrylate, and lauryl were prepared in the same manner as in 3. After charging 0.8 parts of peroxide, the mixture was stirred for 1 hour. The degree of swelling was 6. Next, add 0.3 parts of PVA to 1 part of water.
4 parts of an aqueous solution was added thereto, and after stirring for 1 hour, the temperature was raised to 60° C. and reacted for 26.5 hours. The results are shown in Table 2. There were no aggregates in the obtained resin particles, which was a good result.

[0030]

Example 6 Similar to Examples 1 to 3, resin particles having a particle size of 0.1 to 0.4 mm obtained by sieving were used as seed particles. Next, 20 parts of the above seed particles and low polymerization degree polyvinyl alcohol (polymerization degree 100) were added to 100 parts of water.
, degree of saponification 70-95 mol%) in Examples 1-
Prepare in the same manner as 3, and add N-phenylmaleimide 7.
After charging a monomer mixed solution in which 20 parts of acrylonitrile, 23 parts of styrene, 50 parts of vinylidene chloride, and 0.065 parts of 1,6-hexanediol diacrylate were dissolved, and 0.8 parts of lauryl peroxide, 1 Stir for hours. The degree of swelling was 6.

Next, an aqueous solution of 0.3 parts of PVA dissolved in 14 parts of water was added, and after stirring for 1 hour, the temperature was raised to 60°C.
．． The reaction took place for 5 hours. The results are shown in Table 2. In both Examples 5 and 6, the critical swelling degree showed the same value as in Example 1. There were no aggregates in the obtained resin particles, which was a good result.

[0032]

[Example 7] In the same manner as in Examples 1 to 3, resin particles having a particle size of 0.1 to 0.4 mm obtained by sieving were used as seed particles. Next, 14 parts of the above seed particles and low polymerization degree polyvinyl alcohol (polymerization degree 100) were added to 100 parts of water.
, degree of saponification 50-70 mol%) in Examples 1-
A monomer mixture solution containing 7 parts of N-phenylmaleimide, 20 parts of acrylonitrile, 23 parts of styrene, 50 parts of vinylidene chloride, and 0.065 parts of 1,6-hexanediol diacrylate was prepared in the same manner as in Step 3, and lauryl peroxide was added. After charging 0.8 parts of oxide, the mixture was stirred for 1 hour. The degree of swelling was 8. Next, add 0.3 parts of PVA to 14 parts of water.
After stirring for 1 hour, the mixture was heated to 60° C. and reacted for 26.5 hours. The results are shown in Table 2. The limit swelling degree was 11. There were no aggregates in the obtained resin particles, which was a good result.

[0033]

[Example 8] A solution prepared by dissolving PVA as a suspending agent in 100 parts of water was charged into a reaction vessel, and then 7 parts of N-phenylmaleimide, 20 parts of acrylonitrile, and 2 parts of styrene were charged.
3 parts, 1,6-hexanediol diacrylate 0.0
Pre-dissolved in a mixed solution of 6 parts, and further added 5 parts of vinylidene chloride.
A monomer mixture of 0 parts and 0.8 parts of lauryl peroxide as a radical initiator were charged. After purging with nitrogen, stirring was started, the temperature was raised to 60°C, and the reaction was carried out for 26.5 hours. The resulting resin particles were separated by filtration, washed with water and dried. The residual monomer content in the obtained resin particles was all 0.5% or less, and the polymerization rate was 98% or more.

[0034] The particle size obtained by sieving is 0.1 to 0.
The gel fraction and limit swelling degree of 3 mm resin particles are as follows.
Content Gel fraction
Limit swelling degree 0.1mm~0.2mm:
31% 1%
8 0.2mm~0.3mm: 69%
2% 8 Next, dissolve 0.005 parts of low polymerization degree polyvinyl alcohol (degree of polymerization 100, degree of saponification 50 to 70 mol%) in 100 parts of water, and charge 20 parts of the above resin particles as seed particles into a reaction vessel. , further, 7 parts of N-phenylmaleimide, 20 parts of acrylonitrile, 23 parts of styrene, 50 parts of vinylidene chloride, and 0.0 parts of 1,6-hexanediol diacrylate.
A monomer mixed solution dissolved in 0.065 parts and 0.8 parts of lauryl peroxide were added, and the mixture was stirred for 1 hour. The degree of swelling was 6. Next, add 0.3 parts of PVA to 14 parts of water.
After stirring for 1 hour, the mixture was heated to 60° C. and reacted for 26.5 hours. The results are shown in Table 2. Although 2% of aggregates were mixed in the obtained resin particles, the results were good.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

Effects of the Invention According to the present invention, partially crosslinked amorphous vinylidene chloride resin particles having a relatively large particle size and a spherical shape can be easily produced at a high yield, and the particle size distribution can also be improved. can be easily controlled. The resin particles thus obtained are useful as raw material resin particles for manufacturing foam molded articles.

Claims (1)

[Claims] [Claim 1] Amorphous vinylidene chloride-based resin particles are used as seed particles, and a copolymerizable unsaturated monomer and crosslinking agent mainly composed of vinylidene chloride in an amount such that the degree of swelling is equal to or less than the limit swelling degree of the seed particles. and a polymerization initiator in the seed particles in the presence of low polymerization degree polyvinyl alcohol, and aqueous suspension polymerization in the presence of a suspension stabilizer. Production method