JPS60156736A - Primarily expanded particle of styrene based resin and production of expansion molded article - Google Patents

Abstract

PURPOSE:Expanded particles, obtained by heating specific expansible styrene based resin particles at a specific temperature, and primarily expanding at a low temperature with small energy consumption. CONSTITUTION:Expanded particles obtained by heating expansible styrene based resin particles prepared by impregnating a copolymer, constituted of a styrene based monomer and an acrylic acid ester and/or methacrylic acid ester, and having 60-97 deg.C second order transition temperature with an organic foaming agent with a heating medium at 60-100 deg.C. Warm water is used as the heating medium, and the particles are packed in a mold and hot molded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing primary foamed particles of a styrenic resin and a foamed molded article that are foamed at a relatively low temperature.

Conventionally, propane and butane were used for styrene resin particles.

Expandable styrenic resin particles containing an organic blowing agent such as pentane or dichlorofluoromethane are generally heated with water vapor to form primary expanded particles.

By filling this into a closed mold cavity and heating it with steam, the -F-sub-expanded particles are fused to form a foamed molded article.

Although this conventional method of producing a foamed molded article using steam is the most common method, it also has the following drawbacks.

(1) The temperature of secondary foaming by water vapor (110°C to 125°C) is high.

(2) It is essential to use water vapor as the heating medium during foam molding, and the molding temperature (110 to 125°C) is high, resulting in large energy consumption.

(3) Therefore, since the mold temperature becomes high, the amount of cooling water used is large.

For this reason, the energy cost of one foam molded product is approximately 4.
It is said to be ~50%.

The present invention solves these problems and relates to a method for producing a styrene resin foam that consumes less energy.

That is, the first invention is made by impregnating an organic blowing agent into a copolymer composed of a styrene monomer and an acrylic ester and/or a methacrylic ester and having a secondary transition temperature of 60 to 97°C. 6 expandable styrene resin particles
The present invention relates to a method for producing primary expanded particles of styrenic resin, which is characterized by heating with a heating medium of 0 to 100°C.

The styrenic monomer in the present invention refers to styrene, α-
It is a styrene monomer containing 50% by weight or more of styrene derivatives such as methylstyrene, vinyltoluene, and chlorostyrene, and also contains styrene or styrene derivatives of vinyl cyanide monomers such as acrylonitrile, vinyl acetate, and vinyl chloride. It may also contain copolymerizable monomers. When two or more of these monomers are used, they are not necessarily used in combination, but may be used separately.

It is copolymerized with the styrene monomer in the present invention. The acrylic ester monomer and methacrylic ester monomer are 1, for example, methyl acrylate.

Acrylic esters such as ethyl acrylate, propyl acrylate, butyl acrylate, hexyl acrylate, and octyl acrylate, and methacrylic esters include methyl methacrylate, ethyl methacrylate, propyl methacrylate, and methacrylic acid. Butyl, hexyl methacrylate.

Octyl methacrylate, dodecyl methacrylate.

These include octadecyl methacrylate. These monomers can be used alone or in a mixture of two or more types. The above copolymer is composed of the above styrene monomer, an acrylic acid ester, and a methacrylic acid ester. The next rearrangement temperature is in the range of 60 to 97°C. The preferred secondary transition temperature from the viewpoint of foaming performance and molded product performance is 75 to 9.
It's 0℃. if.

If the secondary dislocation temperature exceeds 97°C, it becomes difficult to produce a molded body using hot water. Further, if the temperature is lower than 60°C, the mechanical strength of the foamed molded product is low and is not practical.

Secondary rearrangement temperature is the residual monomer in the copolymerization body particles.

If foaming agents, plasticizers, etc. are included, the measured value will fluctuate greatly, so it is necessary to remove these fluctuation factors.
6ru. The method is 9. First, place a small lid (2 to 5 durams) of resin particles in a container such as a petri dish.

9t1. The sample was placed in a vacuum dryer at 18Q to 220°C, pretreated for 4 to 6 hours at a vacuum degree of 30 mmHg or less, and then used as a sample for measuring the secondary dislocation temperature.

Methods for measuring the secondary dislocation temperature include a method using a differential calorimeter (DEC) and a method using a thermophysical tester (TMA).

=5- In order to adjust the secondary transition temperature of the above copolymer to 60 to 97°C, styrenic monomer, acrylic ester and/or
Alternatively, the type 11 of the methacrylic acid ester and the amount to be used are determined as appropriate; although the amount to be used cannot generally be determined, the styrenic monomer is approximately 95 to 50% by weight.

Bulk polymerization is often used to produce the above copolymers.

Although any polymerization method such as solution polymerization or suspension polymerization can be employed, the suspension polymerization method is most preferable because it can obtain a copolymer in the form of spherical particles.

Suspension polymerization is carried out in an aqueous medium, and in that case, a sparingly soluble inorganic substance, an anionic surfactant, a water-soluble polymer dispersant, etc. can be used as the dispersant.

Generally speaking, there are 1 well-known poorly soluble inorganic substances.
Can be used for historical purposes. Examples include calcium phosphate, hydroxyapatite, magnesium phosphate, and magnesium pyrophosphate.

The sparingly soluble inorganic substance dispersant is a dispersing agent for styrenic resin particles obtained in an aqueous medium (meaning the total amount of styrenic hexamer, acrylic acid ester, and methacrylic acid ester at the time of preparation; the same applies hereinafter). hand.

It is used in the range of o, ooi to 5 layers and 1 inch. 0.01 heavy i! : If less than % is used, it is difficult to function as a dispersant.

In addition, if the amount exceeds 1:% by weight, the effect as a dispersant will be too strong, and the particles produced will be small and the required particle size (
It is not only difficult to obtain 0.1-4 mm) in good yield, but also emulsification may occur in some cases.

I cut it. #It is essential to have an anionic surfactant present at the same time as a soluble inorganic dispersant; if the anionic surfactant is not present, it will not function as a dispersant.

As the anionic surfactant, commonly known ones can be used. For example, sodium alkylbenzene sulfonate, sodium α-olefin sulfonate, sodium alkyl sulfonate, and the like.

The anionic surfactant is used in an amount of 0.0001 to 0.021 fit% based on the styrenic resin particles obtained in the aqueous medium. If it is used outside this range, it will hardly function as a dispersant.

As the water-soluble polymer dispersant, generally well-known ones can be used. Examples include partially saponified polyvinyl alcohol, alkylcellulose, hydroxyargyl alcohol, carboxyalkylcellulose, polyacrylamide, sodium polyacrylate, polyvinylpyrrolidone, and the like.

The amount of water-soluble polymer dispersant to be used cannot be unambiguously determined because the dispersion effect varies greatly depending on its type, but it is approximately 0.0001 to 3M based on the obtained styrene resin particles in the aqueous medium. Used within a range of quantities. o, o
If the weight is less than ooi, it is difficult to function as a dispersant. In addition, if it exceeds 3% by weight, the effect as a dispersant will be too high, and the particles produced will be small and the required particle size (0.1-4
mm) in good yield.

In some cases, it can also be emulsified.

Further, the aqueous medium is used in an amount of about 80 to 300 weight percent, preferably about 100 weight percent or less, based on the styrenic resin particles obtained.

Polymerization initiators used in copolymerization include benzoyl peroxide,
Organic peroxides such as butyl perbenzoate.

Polymerization initiators generally used for radical polymerization of styrene spinning wheel covers can be used, such as azo compounds such as azobisisobutyronitrile and azobisdimervaleronitrile.

The polymerization initiator is based on the total amount of the styrene monomer and the acrylic ester monomer and methacrylic ester monomer copolymerized therewith.

About 0.1-5% by weight is used.

Next, the organic blowing agent used in the present invention has the property of not dissolving the styrenic polymer produced or only slightly swelling it, and its boiling point is higher than the softening point of the produced polymer. Those that are liquid or gaseous at room temperature can be used.

Examples include aliphatic hydrocarbons such as evapropane, butane, and pentane, and cyclic aliphatic hydrocarbons such as cyclobutane and cyclopentane. When turbidly polymerizing a styrene monomer, an acrylic ester, and a methacrylic ester, the organic blowing agent can be added (press-injected) to the polymerization system during or after the completion of the polymerization reaction for impregnation.

Among the above aC blowing agents, when propane and butane are used alone or in combination, a small amount of a solvent necessary for slightly softening the styrenic resin can be impregnated. Examples of such solvents include ethylbenzene, benzene, toluene, xylene, ethylene dichloride, trichloroethylene, tetraethylene, cyclohexane, and the like. The amount used is 0.1 to 4% by weight based on the styrene resin particles obtained.

Impregnation with an organic blowing agent or other known methods can be used.

The expandable styrenic resin particles obtained as described above can be made into primary expanded particles by heating and foaming them with a heating medium at 60 to 100°C, particularly 60 to 95°C. As described above, in the present invention, primary foaming can be performed at a lower temperature. In particular, by using hot water as the heating medium, energy consumption can be reduced compared to steam heating, which uses water heated to 110°C to 125°C. . As for the heating method.

The expandable styrene resin particles and hot water may be brought into direct contact. Alternatively, the heating can be carried out by placing the 9 expandable resin particles in a foaming tank, reducing the pressure in the core hinoki, and blowing steam at 80 to 90°C into this.

In the second invention, the expandable styrenic resin particles or the sub-expanded particles thereof according to the first invention are filled into a mold, and
The present invention relates to a method for producing a styrenic resin foam molded article, which is characterized by carrying out heat molding using a heating medium of 00°C.

As for the mold, one that is completely closed may be used, but it is also possible to use one that has a large number of fine ventilation holes through which the expandable styrene resin particles or the sub-expanded particles thereof do not pass through. . Conventionally, molds for producing foam molded bodies by heating with steam can be used. As for the heating method.

9. A mold filled with expandable styrene resin particles or sub-expanded particles thereof may be immersed in the heating medium.9. A chamber is provided around the mold where the heating medium flows in and out.

A heating medium may be allowed to flow in and out of this.

The heating medium may flow in and out of a steam chamber attached to a conventional steam heating mold.

As a heating medium, 60 to 100°C, especially 60 to 95°C
You can use hot water. As a result, compared to the conventional case of using steam at 110 to 125 degrees Celsius,
You can save energy. As a heating method, an inlet/outlet chamber for a heating medium may be attached to the mold, and steam at 80 to 90° C. may be introduced into the chamber under reduced pressure.

As described above, according to the second invention, compared to the prior art.

A styrenic resin foam molded product can be obtained with lower energy.

Next, examples of the present invention will be shown.

Example 1 4I! ion-exchanged water 1 in an autoclave with a rotating stirrer.
, 1009. 22 g of tricalcium phosphate, 1 t aqueous solution of sodium dodecylbenzenesulfonate, a, ag, styrene 9009. Acrylic acid n-butyl ester 100
9. Benzoyl peroxide 3.09° Butyl perbenzoate 0.
After 1 hour, the temperature was raised to 90°C while stirring. Thereafter, polymerization is continued while maintaining the temperature at 90°C. A portion of the suspension is sampled from time to time, and the specific gravity of the oil droplets is measured by the specific gravity liquid method to check the single polymerization conversion rate. Polymerization conversion rate is 9
When it reaches 5% or more, add 5g of benzene.

After another 20 minutes, 180 mJ of butane gas was injected under pressure with nitrogen gas. After the injection of butane was completed, the temperature began to rise again.

After 2 hours, the temperature was raised to 120°C, and stirring was continued at this temperature for 4 hours. After that, it was cooled to 30℃, the excess gas in the system was discharged, and the particle size was classified by f3 and 9 after drying.
Expandable styrenic resin particles of uniform size (1.20 mu+diameter) were obtained. This material was aged for 2 days in a 10° C. cold storage, and then immersed in 75° C. warm water to undergo primary foaming to a bulk ratio of 60 times. Next, after air drying at room temperature for 24 hours, the mold (
It was filled into a container (made of aluminum, 5 mm thick, with an internal volume of 100 mm x 100 mm x 40 mm, and having 20 1.0 φ holes on each side) and placed in hot water at 85° C. for 2 minutes.

Next, when the mold was placed in cold water at 13-30℃ for 15 seconds, the mold temperature was 47℃.
It was ℃. The mold was immediately released from the mold to obtain a molded product with a smooth surface and a good melting layer.

Example 2 The same procedure as in Example 1 was carried out except that the amount of styrene charged in Example 1 was changed from 900 g to 9059, and 100 g of n-butyl acrylate was changed to 959 dodecyl methacrylate.

Example 3 The amount of styrene charged in Example 1 was changed to 48309.

Example 1 by changing the amount of n-butyl acrylate to 170g
Expandable styrenic resin particles were synthesized in the same manner as described above. This material was first expanded 60 times in warm water at 65°C. Furthermore, when molded for 2 minutes in hot water at 75° C. in the same manner as in Example 1, a molded product with a clean surface and good fusion bonding was obtained.

Comparative Example 1 The amount of styrene in Example 1 is i, o o o g.

Example 1 except that n-butyl acrylate was not used.
Expandable styrenic resin particles were synthesized in the same manner as described above. This product did not foam at all in hot water at 75°C, and even in hot water at 90°C, the transparent particles slightly turned white and foamed to the extent that they became opaque.

Furthermore, it was not possible to mold the sample in the same manner as in Example 1.

The monomer composition and secondary rearrangement temperature of the styrenic resins in Examples 1 to 3 and Comparative Example 1, the hot water foaming temperature (3 Temperature at which the bulk ratio becomes 60 times when heated in hot water for 1 minute), when the secondary foamed particles (with a bulk ratio of 60 inches) were foam-molded in warm water in the same manner as in Example 1, sufficiently good fusion was achieved. Table 1 shows the minimum temperature at which this occurs (minimum hot water molding temperature) and the temperature at which the mold can be cooled and the molded product removed after foam molding (mold release temperature).

1): from 15-

Claims (1)

[Claims] 1. A copolymer composed of a styrene monomer and an acrylic ester and/or a methacrylic ester and having a secondary rearrangement temperature of 60 to 97°C is impregnated with an organic blowing agent. Expandable styrene resin particles at 60 to io O'C
A method for producing primary expanded particles of styrenic resin, the method comprising heating with a heating medium. 2. The method for producing primary expanded particles of styrenic resin according to claim 1, wherein the heating medium is hot water of 60-100'C. 3. Expandable styrenic resin particles made by impregnating an organic blowing agent into a copolymer composed of a styrene monomer and an acrylic ester and/or a methacrylic ester and having a secondary transition temperature of 60 to 97°C. A method for producing a styrene-based resin foam molded article, which comprises filling a mold with the or-sub-expanded particles thereof and heating and molding them with a heating medium at a temperature of 60 to 100°C. 4. The method for producing a styrenic resin foam molded article according to claim 3, wherein the heating medium is hot water of 60 to 100°C.