JPS5848575B2 - Expandable styrenic resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a foamable styrenic resin composition, and its purpose is to reduce the size of air bubbles generated in the composition when it is heated and foamed. It's about doing.

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, and dichlorofluoromethane, are generally heated with water vapor, etc. After forming pre-expanded particles in which small bubbles (cells) are formed, the pre-expanded particles are filled into a closed mold cavity and heated to cause the pre-expanded particles to further expand and fuse together. The foamed styrene molded product is then made into a molded product.

The keepsake foam produced in this way is used for food containers, cushioning materials, insulation materials, fishing boxes, floats, etc., but product characteristics such as molding time, strength, and surface condition are limited by the air bubbles during foaming. It really depends on the number.

Therefore, in order to impart characteristics suitable for the purpose of use to the shaped body, 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 some of these factors are not clearly defined. Therefore, it is extremely difficult to arbitrarily adjust the number of bubbles.

Therefore, conventional expandable styrenic resin particles generally have the following drawbacks.

(2) 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.
).

Furthermore, since the bubbles are coarse, the bubble film is thick, and residual gas within the bubbles is slow to dissipate during molding, causing expansion and deformation if the molded product is taken out without being completely cooled.

Therefore, it takes a long time to cool down, resulting in poor work efficiency.

Furthermore, since the bubbles are coarse, the surface of the molded product is not smooth, and the cut surface of the cut product molded product also becomes rough.

3) If the manufactured resin particles are stored at a temperature around the summer temperature and then foamed, 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 summer temperature.

The present inventor investigated the number of cells of the expandable snalene resin foam obtained by a conventional method, the period of preparation after production, and the properties of the molded product (
As a result of investigating the relationship between molding time, strength, surface condition, etc., we found that when the bulk ratio during foaming was approximately 60 times, the number of cells per 1 on the cut surface of the foamed particles was in the range of 50 to 300. The aging period after manufacturing is short, the molding time is short, and the strength of the shaped body is strong.

It was confirmed that it has excellent properties as a molded object, with a smooth and beautiful surface and a clean cut surface.

Therefore, we found a method to arbitrarily adjust the number of cells in the foam, and we were able to adjust the number of cells in (d) within the range of 50 to 300. (1) Obtain an expandable styrenic resin with excellent molded properties. As a result of extensive research, we believe that it is possible to
The present invention has been accomplished.

That is, 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 the general formula (1) (wherein R is H or CH3, R' is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 50) as a polymerization component. Regarding.

In the present invention, the styrenic monomer refers to styrene or substituted styrenes such as α-methylstyrene, vinyltoluene, and 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 preferably contained in the range of 6% by weight, especially 0.1 to 2% by weight.
It is preferably contained in a range of % by weight.

Note that if the amount is less than 0.01% by weight, the effect of the present invention will be reduced, and if it exceeds 6% by weight, the number of bubbles will increase (more than 300 cells/mt) and the cell membrane will become thinner. In this case, the water vapor melts the bubble membrane, making cell destruction more likely.

In the general formula (1), the group R is H or CH3, and the group "is,
It is an alkyl group such as methyl, ethyl, proyl, butyl, and n is an integer of 1 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 (I). Vinyl cyanide compounds such as, acrylic esters such as methyl acrylate, ethyl acrylate, butyl acrylate, hydroxyethyl acrylate, methacrylic esters such as methyl methacrylate, ethyl methacrylate, hydroxyethyl methacrylate, vinyl acetate, vinyl chloride, etc. Alternatively, two or more types may be used in combination.

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

The above copolymerization method may be any method such as suspension polymerization, bulk polymerization, solution polymerization, etc.

Suitable polymerization initiators for copolymerization include benzyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-tert-butyl peroxide, 2,5-di(beroxybenzoate)hexyne-3, 1. 3-bis(
tert-butylperoxyisopropyl)benzene, lauroyl peroxide, tert-butyl peracetate, 2,5-dimethyl 2,5-di(tert-butylperoxy)hexene 3,2,5-dimethyl-2,5-di Organic peroxides such as (tertiary butylperoxy)hexane and tertiary butyl perbenzoate, methyl ethyl ketone peroxide, methyl cyclohexanone peroxide, and ab compounds such as azobis-isobutyronitrile and dimethyl azodiisobutyrate. , one or more of these persimmons can be used.

The amount used is determined depending on the type of polymerization component and the desired molecular weight of the resulting polymer, but preferably 0.1 to 4.0 weight yarn is used based on the polymerization component.

In the above copolymerization, when suspension polymerization is carried out, the polymerization is carried out in an aqueous medium. In this case, a sparingly soluble phosphate, a water-soluble polymeric protective colloid, etc. can be added to the polymerization system as a dispersant.

Examples of sparingly soluble phosphates include tricalcium phosphate and 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.

What about poorly soluble phosphates? 0 for the total amount of substances present in the combined system
．． 01% by weight or more, water-soluble polymer protective colloid is 1 to 0
．． Preferably, it is used in a range of 0.001 weight.

In addition, anionic surfactants and water-soluble inorganic salts can be added to the polymerization system.

Regarding the above, organic solvents such as xylene and toluene can be used for solution polymerization.

In addition, during the above copolymerization, polystyrene or styrene-based copolymer particles are suspended in water, heated while stirring, and styrene-based monomer, the compound represented by the general formula (I), and other ingredients as necessary. Copolymerization can be carried out by adding monomers.

Furthermore, after dissolving the styrenic resin obtained as described above in a styrenic 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 styrenic resin used in combination, and has the property of not dissolving the styrenic resin or only causing it to swell slightly. Use what you have.

Examples of such blowing agents include aliphatic hydrocarbons such as propane, butane and penkune, cyclic aliphatic hydrocarbons such as cyclobutane and cyclopenkune, and halogenated hydrocarbons such as methyl chloride and dichlorodifluoromethane. I can do it.

The amount of the blowing agent used is 1 to 20% by weight, preferably 3 to 15% by weight, based on the styrene resin.

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 include ethylene dichloride, trichloroethylene, tetrachlorethylene, benzene, toluene, xylene, ethylbenzene, and the like.

A method of impregnating a blowing agent into a styrenic resin containing the compound represented by the general formula (1) as a component involves adding particles (obtained by suspension polymerization) or pellets of the styrenic resin to an aqueous medium. There are a method in which the foaming agent is suspended in a foaming agent and a blowing agent is force-injected into the suspension, a method in which the styrene resin and the foaming agent are kneaded, and a method in which the styrene resin is immersed in a foaming agent (liquid).

In addition, when the above-mentioned styrene resin is obtained by suspension polymerization, the monomer conversion rate is preferably 50% during the polymerization.
This can be carried out by increasing the blowing agent at a point of % by weight or more.

Note that the resin composition according to the present invention may contain known additives such as pigments, flame retardants, antioxidants, and antistatic agents.

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

As the method, the foaming and molding methods of styrenic resin, which are widely used industrially, can be applied as they are.

For example, if the resin is in the form of particles, it can be pre-foamed with steam and then further steam-foamed in a mold to obtain a shaped product.

Moreover, a foam 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 product immediately after production is large and the size thereof is uniform.

Therefore, the period of precepts is short.

2) When foamed after ripening, the number of cells is large (in the case of a bulk ratio of about 60 times, 1 mm of the cut surface of the foamed particles)
(The number of cells per mold is 50 to 300) Therefore, the cooling period during molding is short and the 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 6 4L autoclave with rotary stirrer Polyvinyl alcohol (Cosenol KH 20, manufactured by Nippon Gokai Chemical Co., Ltd.)
0.005% aqueous solution 1101, styrene 1000g,
Benzoyl peroxide 3.0g, butyl perbenzoate 0.5g
and methoxypolyethylene glycol mecrylate (
n=9 (indicates the number of oxyethylene groups with zero burrs.

Same below. ), NK Ester M-9G (Shin Nakamura Chemical Industry ■Product name)) 10. ? After 1 hour, the temperature was raised to 90°C while stirring.

Thereafter, polymerization is continued while maintaining the temperature at 90°C.

From time to time, 1 part of the suspension is sampled and the specific gravity of the oil droplets is measured by the specific gravity liquid method to check the polymerization conversion rate.

When the polymerization conversion rate reaches 95% or more, polyvinyl alcohol is added to bring the concentration of polyvinyl alcohol in the aqueous layer to 0.
．． Add 20g of ethylbenzene to 4% θ,
After another 20 minutes, 180 rfLl of butane gas is pressurized with nitrogen gas.

After the butane pressure was finished, the temperature started to rise again, and after 1 hour it reached 105%.
°C and continue stirring at this temperature for 6 hours.

After that, the system is cooled to 30℃, the excess gas in the system is discharged, and the particle size (0.84 to 1.197
Particles of a foamable styrene resin composition having a uniform diameter (ft71L diameter) were obtained.

After aging this product in a cold place for 4 days, the bulk ratio is 60.
The mixture was pre-foamed to double its original size, filled into a mold after 24 hours, and molded using a steam molding machine under certain conditions.

Example 2 Methoxypolyethylene glycol mechkryl I-(n
=9, NK ester M-9G, ) instead of methoxypolyethylene glycol methacrylate (n”23-, ■
Ester M-23G (Shin Nakamura Chemical Industry ■Product name)] 1
．． The same procedure as in Example 1 was carried out except that 0.9 was used.

Example 3 Methoxypolyethylene glycol methacrylate (n
=9, 10 g of methoxypolyethylene glycol acrylate [n-4, NK Ester AM-4G (Shin Nakamura Chemical Industry ■trade name)] instead of NK Ester M-9G,)
The same procedure as in Example 1 was carried out except for the use.

Example 4 In Example 1, methoxypolyethylene glycol methacrylate (n = 9) was not dissolved in styrene, but polymerization was started with styrene alone, and when the polymerization conversion rate of styrene was 30% by weight, methoxypolyethylene glycol methacrylate was dissolved. The procedure of Example 1 was followed except that (n=9) was added to the suspension.

Example 5 In a 4-liter autoclave equipped with a rotary stirrer, 0% of polyvinyl alcohol (Ko-Shinanol KH-20, manufactured by Nippon Gosei Chemical Co., Ltd.) was added.
．． 1800g of 3% aqueous solution and polystyrene particles (0.71
~1.0 diameter) was charged, and the temperature inside the system was raised to 80°C while stirring.

110 out of a solution of 420 g of styrene and 15.9 methoxypolyethylene glycol methacrylate (n=9)
Each g was dropped three times at 20 minute intervals.

Next, add 2.10 penduyl peroxide to the remaining monomers.
g, dissolve 0.6 g of tertiary butyl perbenzoate,
The solution was added in the same manner 30 minutes after the first addition of the solution.

After continuing the reaction for an additional 3 hours, the mixture was cooled to obtain vinyl polymer particles having a uniform particle size.

After adding 30 g of ethylbenzene and raising the temperature to 80° C., 250 ml of butane gas was pressurized with nitrogen gas.

Thirty minutes after the end of the butane gas pressure, the temperature started to rise again, and after 2 hours it was raised to 115°C, and stirring was continued for 3 hours while maintaining this temperature.

Thereafter, the mixture was cooled to 30° C., excess gas in the system was discharged, and the mixture was dried in an oven to obtain particles of a foamable styrenic resin composition.

The particles were shaped according to Example 1. Example 6 1,800 g of xylene was placed in a 4-liter four-eye flask, heated to 100°C while stirring through an inert gas, and 1,200 g of styrene and 1 liter of abbisisobutyronitrile were added to it.
A mixed solution of 5 g and 24.9 g of methoxypolyethylene glycol meccrylate (n=9) was added dropwise over 2 hours.

After the dropwise addition, the reaction temperature was raised to 140°C, and the reaction was continued for a further 3 hours, which was then determined as the end point.

Then, the xylol used as a solvent was separated by heat distillation.

After pelletizing the thus-produced styrene resin using a pellet molding machine, 1,500 ml of ion-exchanged water was placed in a 4-liter autoclave equipped with a rotary stirrer. 3.0 g of 9-basic calcium phosphate, 0.15.9 g of sodium dodecylbenzenesulfonate, 45 g of calcium carbonate, and 1200 g of pellets were charged, and the temperature in the system was raised to 80° C. while stirring.

After the temperature was raised, 24.9 ml of ethylbenzene was added, and 210 ml of butane gas was further pressurized with nitrogen gas.

Thirty minutes after the butane gas was turned off, the temperature began to rise again, and after 2 hours, the temperature was raised to 115°C, and stirring was continued for 3 hours while maintaining this temperature.

After that, it is cooled to 30°C, excess gas in the system is discharged,
The powder was dried in an oven to obtain particles of an expandable styrenic resin composition.

The particles were shaped according to Example 1.

Example 7 Expandable styrenic resin composition particles were produced by the method of Example 1, and then tested in accordance with Example 1 with a ripening temperature of 40° C. and a ripening period of 4 days.

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

Comparative Example 2 The same procedure as Example 5 was carried out except that methoxypolyethylene glycol meccrylate was not used.

Comparative Example 3 The same procedure as Example 6 was carried out except that methoxypolyethylene glycol meccrylate was not used.

Comparative Example 4 The same procedure as Example 7 was carried out except that methoxypolyethylene glycol meccrylate was not used.

Table 1 summarizes the characteristic values of the expandable styrenic resin compositions obtained in each of the above Examples and Comparative Examples.

According to the present invention, expandable styrenic resin particles having a large number of cells when formed into a foam can be produced.

The expandable styrenic resin particles made using conventional technology are approximately 60
In the case of a bulk multiple of 1 mt at the cross section of the foam particle?
The number of bubbles per t was 50 or less, but according to the present invention, the number of bubbles increased to 50 to 300.

The increase in the number of cells gives the expandable particles and foamed articles the following features:

(2) 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. In a foamable styrenic resin composition comprising a styrenic resin and a blowing agent, the styrenic resin has a styrene monomer and a general formula (1) (wherein, R is H
or CH3, Rl is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 1 to 50) as a polymerization component.