JPS58120643A - Expandable styrene resin composition - Google Patents

Abstract

PURPOSE:To prepare the titled composition having smooth and beautiful surface and high strength, and containing fine bubbles, by copolymerizing a styrene monomer with a specific vinyl compound and foaming the copolymer with a foaming agent. CONSTITUTION:A styrene-type monomer such as styrene (>=50wt%), is mixed with a compound of formula (R is H or CH3; R' is 1-4C alkyl; n is integer of 1-50) and copolymerized. The copolymer is mixed with a foaming agent (e.g. methyl chloride) and foamed by heating to obtain the objective product. A vinyl monomer other than styrene (e.g. acrylonitrile) may be used as a copolymerizing component in combination with the above components.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foamable styrenic resin composition, and an object of the present invention is to heat the composition to foam it and reduce the size of the air bubbles generated in the composition. Toni 7bru.

Conventionally, expandable styrenic resin particles, which are made by impregnating styrene resin particles with easily volatile blowing agents such as propane, butane, pentane, [methyl chloride, dichlorofluoromethane, etc.], are generally heated with water vapor, etc. The pre-expanded particles are made into nine pre-expanded particles by generating small cells (cells).The pre-expanded particles are then filled into a closed mold cavity and heated to make the pre-expanded particles further foam and at the same time fuse together. This makes a foamed styrene-based molded product according to the mold. The 9-molded foam made in the same way is used for food containers, cushioning materials, insulation materials, fishing boxes, floats, etc., and the molding time of this material is 9. Strength 1.
Product properties such as surface condition are greatly influenced by the number of cells during foaming. However, in order to impart round physical properties to the molded product suitable for the intended use, it is necessary to arbitrarily adjust the number of cells in the foam. However, the factors governing the number of bubbles are influenced by the type, content, and impregnation temperature of the blowing agent, as well as the degree of polymerization of the styrene resin and other factors, and these factors are not clearly defined. Therefore, the number of bubbles can be set arbitrarily K111
It is fundamentally difficult to articulate. Therefore, conventional expandable styrenic resin particles generally have the following drawbacks.

l) When resin particles are foamed immediately after production, the number of cells in the cross section of the foam is small and their sizes are non-uniform. Therefore, after production, a long aging period is required until the size of the bubbles becomes uniform.

2) When foaming is performed after aging, the size of the bubbles becomes uniform, but the number of bubbles is small (if the bulk ratio is about 60 times, the number of bubbles per 1 × 1 on the cut surface of the foamed particle is 50 or less)
. i9 Because the bubbles are coarse, the bubble film is thick, and the residual gas in the bubbles dissipates slowly during molding, causing expansion and deformation if the molded product is taken out without being completely cooled.As a result, cooling takes a long time. It is time consuming and the work efficiency is low.Furthermore, the rounding process has coarse air bubbles, the smoothness of the surface of the molded product is affected, and the cut surface of the cut product molded product also becomes rough.

3) If the manufactured resin particles are stored at a temperature similar to the summer temperature and foamed after 9 days, the bubbles on the cut surface of the foam will become rough, so it is necessary to store it in a cold storage at a temperature below the seasonal temperature.

The present inventor investigated the number of cells of expandable styrenic resin foam obtained by a conventional method, the aging period after production, and the molded product characteristics (
Regarding the relationship between molding time, strength, surface condition, etc. - Comparing the results when the bulk ratio at one time of foaming is about 60 times, the number of bubbles in 1 on the cut surface of the foamed particles is in the range of about 50 to 300. We confirmed that the product has excellent properties as a molded product, such as a short aging period after production, a short molding time, strong molded product strength, a smooth and beautiful surface, and a clean cut surface. Therefore, if we find a method to arbitrarily adjust the number of cells in the foam, and if we can adjust the number of cells in 13 within the range of 50 to 300, it will be possible to obtain a foamable styrenic resin with excellent round-bottom properties. With this in mind, we have conducted extensive research, and as a result, we have come up with the present invention.

That is, 1 the present invention provides a foamable styrenic resin composition comprising a styrenic resin and a blowing agent, in which the styrenic resin contains a styrenic monomer and a general formula (1) (wherein RFiH or CHs 6!, R' is an alkyl group having 1 to 4 carbon atoms, and n is 1.

It is a substituted styrene based on chlorostyrene.

The compound represented by the general formula +1) to be copolymerized with the styrene monomer is contained in the styrene resin as a component of 0.01 to
It is preferable to include a range of 6-weight, especially KO, 1 to 2
Preferably, the weight range is 0.01
If the weight is less than -, the effect of the present invention will be small), but if it exceeds 6 -, the number of bubbles will be too large (300 or more) and the bubble film will become thin.

During molding, the oxygen bubble film is melted by water vapor, forming celery and group R'
is an alkyl group such as methyl, ethyl, propyl, butyl, and is an integer of n1jl to 50.

The styrenic resin of the present invention can be obtained by copolymerizing a styrene monomer and a compound represented by the general formula +11. vinyl compound.

Methyl acrylate, ethyl acrylate.

Acrylic acid esters such as butyl acrylate and hydroxyethyl acrylate, methyl methacrylate, ethyl methacrylate, and humans.

One or more of methacrylic acid esters such as loxethyl methacrylate, vinyl acetate, and vinyl chloride may be used in combination.

The above-mentioned styrene resin preferably contains 50 weight or more of a styrene monomer in its constituent components from the viewpoints of expansion ratio, fusion of molded articles, surface appearance, and cycle quality.

The above copolymerization methods include suspension polymerization and bulk polymerization.

Solution polymerization etc. are optional.

Suitable polymerization initiators for copolymerization include:

Benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, Su5
-di(peroxybenzoate)hexyne-3,1,3
-bis(tert-butylberoxyingrobil)benzene.

lauroyl peroxide, tert-butylberacetate, s5
-dimethyl-25-di(tert-butylperoxy)hexane-L 2.5-')l methyl-45-di(tert-butylperoxy)hexane and tert-butylberbenzoate, methyl ethyl ketone peroxide, methyl cyclohexanone peroxide, etc. Organic peroxide, azobis-
One or more of these compounds can be used, such as isobutyronitrile and dimethyl azodiisobutyrate. The amount used is determined by the aI@ of the polymerization component and the desired molecular weight of the resulting polymer, but it is preferable that the polymerization is carried out in the polymer, in which case a releasable phosphate is used as a dispersant. , a water-soluble bulk molecule protective compound, etc. can be added to the polymerization system.

Stile, tricalcium phosphate as a poorly soluble phosphate.

Examples include magnesium phosphate. Examples of polymeric protective colloids include polyvinyl alcohol, water-soluble cellulose derivatives such as alkyl cellulose, hydroxyalkyl cellulose, and carboxyalkyl cellulose, and sodium polyacrylate. The amount of soluble phosphate is α01 weight or more based on the total amount of substances present in the polymerization system.

The water-soluble polymeric protective colloid is preferably used in an amount of 1 to 0.001 weight. In addition, anionic surfactants and water-soluble inorganic salts can be added to the polymerization system.

In the above, K that undergoes solution polymerization is xylene.

Organic solvents such as toluene can be used.

In addition, during the above copolymerization, polystyrene or styrene copolymer particles are suspended in water, heated while stirring, and the styrene monomer is further added to the styrenic resin obtained as described above. After dissolving in the monomer, the styrenic resin of the present invention can be finally obtained by suspension polymerization, bulk polymerization, solution polymerization, etc.

The blowing agent, which is a component of the present invention, has a boiling point lower (than the softening point of the styrene resin used in combination) and has the property of not dissolving the styrenic resin or causing only slight swelling. Use four 7'l's. Such blowing agents include aliphatic hydrocarbons such as propane, butane, and pentane, cyclic aliphatic hydrocarbons such as cyclobutane and cyclopentane, and halogenated hydrocarbons such as methyl chloride and dichlorodifluoromethane. can be mentioned. The amount of blowing agent used is 1 to 20 per styrene resin.
The ratio is high, preferably 3 to 15% by weight.

Among the above blowing agents, when propane and butane are used alone or in combination, it is preferable to use a small amount of a polystyrene or styrene copolymer solvent. Examples of such solvents are ethylene dichloride, trichlorethylene, ? ) 9 A method of impregnating a blowing agent into a styrene-based resin using chloroethylene, benzene, toluene, xylene, ethylbenzene, etc. is a method of impregnating styrene-based resin particles (obtained by suspension polymerization) or pelletizing them into aqueous styrene-based resins. Suspend in medium.

There are methods such as press-fitting a foaming agent into the foam, kneading the styrene resin and the foaming agent, and immersing the upper styrene resin in the foaming agent (liquid). First, when the styrenic resin is obtained by suspension polymerization, a blowing agent can be press-injected during the polymerization, preferably at a point when the monomer conversion rate is 50 weight or more.

In addition, M material is added to the resin composition related to IMK.

- Known additives such as refractory agents, antioxidants, and antistatic agents may be included.

Foaming of the expandable styrenic resin composition according to the present invention is carried out by methods such as heating and reduced pressure.

This method is widely used industrially to produce styrene resin. The molding method can be applied as is.For example, if the resin is in the form of particles, after pre-foaming with water vapor,
Steam foaming is further carried out in the mold, and a molded product can be obtained.

Foams can also be obtained using an extrusion foaming machine.

The expansion ratio of the expandable styrenic resin composition according to the present invention can be arbitrarily selected from a low ratio to a high ratio.

The expandable styrenic resin composition according to the present invention has the following features.

1) The number of cells in the cross section of the foamed material after foaming is large and the size thereof is uniform. Therefore, the ripening period is short.

2) When foaming after aging, the number of cells is large (approximately 60
In the case of bulk multiple of 9 times, 1■1 on the cut surface of expanded particles
(The number of cells in this case is 50 to 300) Therefore, the cooling time during molding is short and work efficiency is high. The surface of the molded product is smooth and beautiful, and the cut surface of the cut molded product is also clean.

Next, examples of the present invention will be shown.

Example 1 Polyvinyl alcohol (Gohsenol KH-20, E1 butyl acetate 0.5? and methoxypolyethylene M-9G (Shin Nakamura Chemical Industry ■ trade name)) IOP was placed in a 4 g autoclave with a rotary stirrer and stirred. While stirring, the temperature was raised to 90°C after 1 hour. Thereafter, polymerization is continued while maintaining the temperature at 90°C.

Once in a while, a portion of the suspension is t-plumped and the specific gravity of the oil droplets is measured using the specific gravity liquid method to check the conversion rate of one polymerization.

When the polymerization conversion rate reached 95 or more, 7:f-1 was added to the polyvinyl alcohol to dilute the polyvinyl alcohol 11 and 7 in the aqueous layer.
After setting α to 4%, 20f of ethylbenzene was added,
After another 20 minutes, butane gas 1801 is pressurized with nitrogen gas. After the injection of butane was completed, the temperature started to rise again, and after 1 hour, the temperature was raised to 105°C, and stirring was continued at this temperature for 6 hours. After this, particles of the expandable styrene resin composition were obtained at a temperature of 30°C.

This product is aged in a cold place for 4 days, and after 9 days, the bulk multiple is 60.
The foam was pre-foamed to double its original size, and after 24 hours it was heated with 11K gold and molded using a steam molding machine under certain conditions.9.

...] instead of methoxypolyethylene glycol methacrylate (n=23.NK varnish #@Me・)
Instead, methoxypolyethylene glycol acrylate (n = 4. NK Ester Example 4 In Example 1, methoxypolyethylene glycol methacrylate) (n = 9) was not dissolved in styrene and polymerization was initiated with styrene alone. The procedure was as in Example 1 except that methoxypolyethylene glycol methacrylate (n=9) was added to the suspension when the polymerization conversion rate of styrene was 30% by weight.9.

Example 5 An α3-aqueous solution of polyvinyl alcohol (Go-Shinanol KH-20.E3 Honsei Kagaku Co., Ltd.) (1800) and polystyrene particles (α71-
1050P (10m11 diameter) was charged, and the temperature inside the system was raised to 80°C while stirring. Styrene 420? and methoxypolyethylene glycol methacrylate) (n=
9) 110P out of 152 solutions 3 times at 20 minute intervals
The solution was added in the same manner 30 minutes after the third addition of the solution. After continuing the reaction for an additional 3 hours, the mixture was cooled to obtain vinyl polymer particles having a particle diameter of 90 mm.

Ethylbenzene SO was added thereto, the temperature was raised to 80°C, and after 9 days, butane gas 250117 was injected under pressure with nitrogen gas. 30 minutes after the end of butane gas injection.

After 2 hours, the temperature was raised again to 115°C, and stirring was continued for 3 hours while maintaining this temperature. Thereafter, the mixture was cooled to 30° C., the excess gas in the system was discharged, and the mixture was dried separately by F to obtain particles of an expandable styrene resin composition. These particles were molded according to Example 1.

Example 6 Kijirol 180 (1) was placed in a 4 g four-bottle flask and heated to 100°C while stirring with inert gas, and styrene 1200 Ff and Azovin? After adding 90 drops of the mixture over 2 hours, the reaction temperature was raised to 140°C.
The time reaction was continued and the end point was set after 9 days. Next, Kukijirol was used as a solvent and separated by heating distillation.The styrene resin thus produced under pressure was pelletized using a pellet molding machine, and then placed in an autoclave equipped with a rotary stirrer with 1500 ml of ion-exchanged water. ) Basic calcium phosphate 3
．． 0fP and sodium dodecylbenzenesulfonate 0.
15), Calcium carbonate 4.5 F Toberet 120
Charge 0F and raise the temperature in the system to 80℃ while stirring. Noboru am, ethylbenzene 24? Then, 2101 Llt of butane gas and nitrogen gas were injected under pressure. After 30 minutes of butane gas injection, the temperature started to rise again, and 2 hours later, 1
The temperature was then maintained at 15°C and stirred for 3 hours. After that, the mixture was cooled to 30°C and the excess gas in the system was discharged.
It was dried separately by F to obtain particles of an expandable styrenic resin composition. The particles were molded according to Example IK.

Example 7 Expandable styrenic resin composition particles were produced by the method of Example 1, and then aged at a temperature of 40°C.

A test was carried out according to Example IK, with the aging period being 4 days.

Comparative Example 1 The same procedure as Example 1 was carried out except that methoxypolyethylene glycol methacrylate was not used.

Except for this, the same procedure as in Example 5 was carried out.

The same procedure as in Example 6 was carried out except for the above.

Everything else was the same as Example 7.

The characteristic values of the expandable styrenic resin compositions obtained in each of the above Examples and Comparative Examples are summarized in ilK.

According to this invention, it is possible to produce expandable styrenic resin particles having a large number of cells when formed into a 9-foamed product. When the expandable styrenic resin particles made by the conventional technology have a bulk ratio of about 60 times, the number of bubbles in the cut surface of the expanded particles is 50 or less, and the number of bubbles in the foam particles according to the present invention is 50 or less. The number is 5
As the number of cells increases from 0 to 300, the following 4I lengths are added to the expandable particles and foam molded products.

1) The aging period of expandable particles can be shortened.

2) Molding time can be shortened.

3) The strength of the foamed molded product increases.

4) The surface of the foam molded product is smooth and beautiful.

Claims (1)

[Claims] 1. Nl foam containing a styrene resin and a blowing agent
In the styrenic resin composition, the styrenic resin is a styrenic monomer and a compound of the general formula (1) (in formula 1, R is H or CHa and LJ).