JPS5984932A - Production of thermoplastic resin particle - Google Patents

Abstract

PURPOSE:To produce expandable thermoplastic resin particles having improved heat resistance and moldability, by treating particles of a specific styrene-maleic anhydride copolymer with a vinyl aromatic monomer and a specific compound in an aqueous medium, and adding a foaming agent to the treated particles. CONSTITUTION:Particles of a styrene-maleic anhydride copolymer, containing 15-30wt% maleic anhydride, and having >=500 average polymerization degree are suspended in an aqueous medium with a dispersing agent, e.g. partially saponified polyvinyl alcohol (PVA), and a solution of a compound of the formula RX (R is a functional group reactive with dicarbonyloxo group; R is an aliphatic residue having one double bond), e.g. glycidyl methacrylate, in a vinyl aromatic monomer, e.g. styrene, is added to the suspension. The resultant mixture is then polymerized in the presence of a polymerization catalyst, e.g. benzoyl peroxide, in the suspension state, and a foaming agent, e.g. propane, is added to the suspension during or after the polymerization to produce the aimed thermoplastic resin particles containing 3-12wt% maleic anhydride component.

Description

[Detailed description of the invention] This invention relates to a method for producing thermoplastic resin particles.

More specifically, the present invention provides for
Average degree of polymerization is 50 with a maleic anhydride content of 5-80% by weight.
0 or more styrene-maleic anhydride copolymer resin particles,
In the presence of a polymerization catalyst, vinyl V aromatic monomer and formula 1tx (
In the formula, X is a radical (a functional group that reacts with a diM oxo group, R
is an aliphatic residue having one double bond), and by adding a blowing agent during or after the treatment to form foamable thermoplastic resin particles ( To) I'm impressed with the method for producing fat particles.

Polystyrene resin is used for molding and foaming materials.
Although it is widely used as a fat, it has a low heat distortion temperature.
While they cannot be used in applications requiring heat resistance, styrene-maleic anhydride copolymer resins generally have a high heat distortion temperature. However, at present, in order to make the maleic anhydride component uniformly distributed in the molecular chain, and to make it a polymer, it is extremely difficult to control the reaction, requiring complicated methods and making it expensive. Furthermore, when this copolymer resin is used in an extruder and re-pelletized, the re-pellet obtained tends to shrink when heated, so it is not possible to make this sheet into a sheet. When molded, it was very difficult to mold because it was easily stretched during sheet extrusion.

Further, when the pellet was foam-molded using expandable particles containing a foaming agent, the molding process was narrow.

The inventors of this invention, as a result of intensive studies to solve the problem described above, found that styrene-maleic anhydride co-based resin particles with a high degree of polymerization and a relatively large maleic anhydride component content were dissolved in an aqueous medium. A compound having a functional group and a double bond in the same molecule that can react (ring-opening reaction) with the carboxylic acid anhydride in the molecular chain in the suspension rt+.
A solution of a vinyl aromatic hexamer is added to the particles to substantially absorb it into the particles, and then the ring-opening reaction and polymerization described below are carried out. In addition, even when this resin is used to form a sheet, thermoplastic resin particles exhibiting good moldability can be obtained. This invention was completed by discovering that it is possible to obtain foamable thermoplastic resin particles with excellent foamability, moldability, and heat resistance.

The styrene-maleic anhydride copolymer resin used in this invention is one containing 15 to 80 parts of hydrated maleic acid. It can be obtained by copolymerization using a known method.

If the maleic anhydride content of this copolymer resin is less than 15% by weight, the same thermal properties as described above cannot be expected, and if it exceeds 80% by weight, it becomes difficult for the vinyl aromatic monomer to enter the styrene-maleic anhydride copolymer particles, which is preferable. As the ustyrene-maleic anhydride copolymer resin, one having a so-called high degree of polymerization is used. The average degree of polymerization used is at least about 500 or more. If a polymer having an average degree of polymerization of 500 or more is used, the resulting resin particles will have low mechanical strength when molded into a molded article, which is not preferable.

These copolymer resins can be used as raw materials for the present invention even if they contain small amounts of additives to improve or impart desired properties. For example, if a small amount of synthetic rubber such as butadiene rubber is added, the one-stroke impact resistance will be improved.

In this invention, the styrene-maleic anhydride copolymer υd fat has a shape of 0.5 mm, such as a pellet shape, a flat shape, or a square shape.
Those having a particle size of about 1 to 10 mm are used.

In this invention, first, the styrene-maleic anhydride copolymer dark fat particles described below are dispersed in one aqueous medium. In this case, a dispersant is usually used. Examples of dispersants include organic compounds such as partially saponified resin, polyacrylate, polyvinyl 7-repyrolidone, carboxymethyl cellulose, methyl cellulose, calcium stearate, and ethylene bisstearamide. Pond, birophosphate fVVum, calcium phosphate, calcium carbonate.

Examples include inorganic compounds consisting of fine powder particles that are sparingly soluble in water, such as magnesium carbonate, magnesium phosphate, magnesium birophosphate, and magnesium oxide. In the method of this invention, when using a compound as a suspending agent, it is preferable to use a surfactant such as sodium dodecylbenzenesulfonate. It is used by adding 0.01 to 6 weight units of f'L.

Next, a vinyl aromatic monomer solution of the binding monomer is added to the suspension.

As the bonding monomer, a compound represented by 2RX (in the formula, X is a functional group that reacts with a dicarbonyloquine group, and 几 is an aliphatic residue having one double bond) is used.

The functional group in the definition of formula group, amide group, epoxy group, etc. The hydroxy group or amide group is preferably bonded to the vinyl group through one or two carbon atoms. Further, the ebok V group may be bonded to the vinyl group through an oxygen atom or a carbon atom. Specific compounds include allylglycidi V ether,
Glycidyl methacrylate, allyl alcohol, N-n
-butoxymethylacrylamide and the like.

These compounds are generally known as polymer modifiers, and compounds similar to these are used.

In this invention, it is preferable to graft at least one graft per molecule of the copolymer resin. Yes
It may be partially crosslinked.

From this point of view, it is desirable to select the amount of the bonding agent used in the present invention depending mainly on the maleic anhydride content in the copolymer resin. The bonding agent is 9ii1. in the copolymer resin. 0.1-2 for water maleic acid component
The amount used is 0.2 to 10 molar, and θI'i < is 0.2 to 10 molar.

The above-mentioned functional group on the bond attacks the carboxylic acid anhydride site in the molecular chain of the styrene-maleic anhydride copolymer to open the ring. As a result, a double bond that can be copolymerized with the vinyl aromatic monomer is introduced into the molecular chain of the copolymer. Examples of the vinyl aromatic monomer used in the present invention include styrene and a-methylstyrene.

A vinyl aromatic monomer containing ethyl styrene, chlorostyrene, bromostyrene, vinyl toluene, vinyl to cinnabar, isopropyl xylene, etc. alone or in a mixture of two or more, and containing 50% by weight or more of these vinyl aromatic monomers. Monomers capable of copolymerization, such as acrylonitrile.

A mixture with methyl methacrylate, methyl acrylate, etc. may also be used.

The weight ratio of the styrene-maleic anhydride a copolymer resin and the vinyl aromatic monomer is selected so that the maleic anhydride content in the resin of the thermoplastic resin particles to be produced is 2 to IO weight ratio. If the content is less than this range, the thermoplastic resin finally obtained will have a low heat deformation temperature, which is not desirable. It becomes difficult to dissolve in the liquid.

This dispersion is then polymerized in suspension in the presence of a winding catalyst. Examples of the polymerization catalyst used in this invention include benzoyl peroxide, tart-butyl perbenzoate, and lauroyl peroxide.

Organic peroxides such as tert-butylperoxy-2-ethylhexanoate and tert-butyl peroxide,
Azo compounds such as azobisisobutyronitrile and azobisdimethymuvaleronitrile can be used.

The polymerization catalyst can be used by being dissolved in the vinyl aromatic monomer together with the binding monomer, or alternatively, it can be used by being dissolved in a solvent such as benzene, toluene, or xylene that does not cause polymerization.

Polymerization is carried out by heating and stirring at a temperature of 66 to 95°C, preferably about 80 to 90°C, for 2 to 12 hours, and further removes a very small amount of residual polymer at a temperature of 120 to 140°C.
℃ to complete the polymerization. Under these conditions, the force V in the molecular chain of the styrene-maleic anhydride copolymer attacks the functional group (ring-opening reaction), polymerization of the styrene monomer, polymerization of the styrene monomer with the double bond in the bonding monomer, and intermolecular crosslinking due to these reactions. Examples include easily volatile blowing agents, i.e., n-aliphatic hydrocarbons such as propane, n-butane, i-butane, n-pentane, i-pentane, n-hexane, and cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane. Examples include halogenated hydrocarbons such as group hydrocarbons, methyl chlorophyte, ethyl chlorophyte, dichlorodifluoromethane, chlorodifluoromethane, and trichlorofluoromethane. These blowing agents are generally used in a proportion of 8 to 40% by weight based on the thermoplastic resin particles, and a small amount of a chemical agent such as toluene or xylene may also be used in combination.

The blowing agent may be added at any time during the polymerization or after the polymerization is complete. Preferably, the product particles are impregnated after the polymerization is completed. To impregnate the thermoplastic resin particles with the blowing agent after completion of polymerization, the dispersion of thermoplastic resin particles obtained above can be directly transferred to an autoclave, or the particles can be taken out and then the dispersant can be impregnated with the blowing agent. This is done by putting an aqueous medium into an autoclave, suspending it, heating it, and pressurizing the foaming agent.

The expandable thermoplastic resin particles obtained as described above are
Separate from water, wash and dry as appropriate before use.

The obtained thermoplastic resin has excellent heat-reducing properties (for example, when re-pelletized, shrinkage due to heat is small) and has good moldability even when made into a sheet using this resin. In particular, when molded, it has excellent foaming properties and heat resistance, and
It shows the characteristic that jJ is wide.

Next, the present invention will be explained with reference to Examples.

Example 1 In a reaction volume of 61° internal volume, 2000 f of water, 4.8 g of metathetical magnesium hyrophosphate, )-deVIV sodium benzenesulfonate 2 qb water? 560f of styrene-maleic anhydride copolymer particles (average degree of polymerization 1000) having a volume of H1oy and a maleic anhydride component content of 18% by weight were added, and while maintaining the temperature at 85°C, benzoyl peroxide 4.
A solution of 2.75 f of glycidyl methacrylate was added dropwise to a solution of 1.1 f of 4f, tθrt-butyl perbenzoate dissolved in styrene monomer (1450 f) over a period of 8 hours, and maintained at 85° C. for an additional 6 hours. 14
The reaction was completed by holding at 0°C for 8 hours.
At 95% weight, the softening point was 112°C.

Further, when the sample was immersed in hot toluene at 180°C, 67 weight of insoluble matter remained.

Example 2 Same as in Example 1 except that styrene monomer 1450f was replaced with 200g of α-methylV styrene, nuclear substituted chloroV styrene 8B Of, and styrene 870fii.
The softening point of the resulting T-resin after reacting under the following conditions was 120'.
Meriyuki in C. Insoluble matter in heated toluene at 80°C is 72% by weight, t0 Example 9 Resin obtained in Example 1 is 1.2 amφ Suri Soto is 8
Extrude from this hole with a hole, and after cooling with water, use a V-tizer to make a diameter of 1.5g111. A pellet with a length of 2.6 mm was obtained. 1,200 y of these pellets were placed in an autoclave with a capacity of 61 kg, water at 2,800 F, and 4 ml of magnesium pyrophosphate using the double decomposition process.
．． 8f, l'Sodium decylbenzenesulfonate 2 weights of sodium decylbenzene sulfonate were added together with the door L/F 48f, and 12 (l) of butane was press-ined while stirring. 85°
After raising the temperature to 80°C and maintaining it for 24 hours, the beads were cooled to 80°C to obtain foaming agent-containing beads.
After dehydration and drying, store at 15°C for 8 days, then store at 100°C.
When foamed with steam, foamed particles having a bulk density of 0.022 k (J/l) were obtained.The foamed particles were left open in a room for 24 hours, and then filled and molded, resulting in a mass of 1.0 kg. /cd to 1.5 k(j/-) gives a good molded body with a specific gravity of 0.028 to 9/(1).
In addition, in Example 4゜W Example 1, in which the length direction was shortened to 2.4 mm when left in a constant temperature bath at 160 ° C. for 24 hours, the amount of glycidyl methacrylate dissolved in the styrene monomer was Softening temperature of resin obtained by reaction under the same conditions except for Tatsumi T and heat 1 of 180 °C
The amount of insoluble matter after immersion in ene was as shown in Table 1.

Table 1゜Example 6゜In Example 1, styrene-maleic anhydride copolymer particles with a maleic anhydride content of 21% by weight were used, and the amount used and the amount of styrene monomer dropped were changed. Table 2 shows the softening temperature of the resin obtained by reacting under the same conditions except for 9, and the weight of insoluble matter after immersion in hot toluene at 180°C.

Table 2゜ Agent Patent Attorney Shintabe Nogawa

Claims (1)

[Claims] 1. In an aqueous medium, styrene-maleic anhydride copolymer resin particles having a maleic anhydride content of 15 to 80% by weight and an average degree of polymerization of 500 or more are suspended in an aqueous medium in the presence of a polymerization catalyst. , treated with a vinyl aromatic monomer and a compound represented by RX (wherein X is a functional group that reacts with a dicarbonyloquine group, and 几 is an aliphatic residue having one double bond),
A method for producing thermoplastic resin particles characterized by adding a blowing agent after treatment to obtain expandable thermoplastic resin particles containing 8 to 12 maleic anhydride components. . 2. The compound represented by formula 1tx is 0.0% relative to the maleic anhydride component in the styrene-maleic anhydride copolymer resin.
8. Vinyl aromatic monomer, compound represented by formula X and polymerization Claim 1 or t is the production according to claim 2, wherein the catalyst is absorbed into styrene-maleic anhydride copolymer resin particles and treated.