JP2006137032A - Manufacturing method of foamed synthetic resin molded product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a foamed synthetic resin molded product by the integral molding of a surface material, to which a vapor hole for introducing an aqueous heating medium can not be formed, and a foam. <P>SOLUTION: The foamed synthetic resin molded product is manufactured by charging foamable synthetic foaming resin particles and water in a mold and heating them by a non-aqueous heating means to perform the foam molding of them. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  A foamed synthetic resin molded article obtained by foaming molding by filling a mold with foamable synthetic resin particles containing moisture inside or coexisting moisture, and then heating by a non-aqueous heating means, and its It relates to a manufacturing method.

Conventionally, in order to mold a foamable synthetic resin in the form of particles (beads) such as a foamable polystyrene-based resin, the foamable synthetic resin particles are filled in a molding die that is closed but not sealed, and then steam, etc. The aqueous heat medium is sufficiently introduced into the molding die through a plurality of vapor holes provided in the molding die, the foamable synthetic resin particles are sufficiently heated, and the mutual foaming is performed. It has been natural to perform foam molding by promoting fusion (for example, see Non-Patent Document 1).
All about Expanded Polystyrene -Technology and Business Basic Knowledge-, Martec Co., Ltd., pp. 98-99, issued on May 1, 1995

  However, in the conventional foam molding method described above, a large amount of water-based heat medium such as water vapor is introduced into the mold and subjected to heat foaming. Therefore, if a large amount of water-based heat medium is not used, foaming is performed. The mutual fusion of the synthetic resin particles is insufficient. Therefore, for example, it is difficult to integrally mold with a surface material that cannot form a steam hole for introducing an aqueous heat medium. For example, when a foamed synthetic resin molded body is formed inside a hollow product and is solid. For example, a synthetic resin foam molded body that matches the hollow shape of the product must be separately molded and inserted to obtain a solid product.

  Also, even if the hollow synthetic product is forcibly filled with foamable synthetic resin particles and foamed, it is only a solid product that has extremely poor strength due to poor mutual fusion due to the absence or lack of aqueous heat medium. Could not be manufactured.

The present invention solves such problems, and is characterized in that foaming molding is performed by filling foamable synthetic foamed resin particles and water in a mold and then heating by a non-aqueous heating means. The present invention relates to a method for producing a foamed synthetic resin molding.
As a preferred embodiment,
(1) The foamable synthetic resin particles containing water are filled in a mold and then subjected to foam molding by heating with a non-aqueous heating means.
(2) formed by using a mold having no vapor holes,
(3) The non-aqueous heating means is a microwave,
(4) The mold is made of a non-metallic material.
(5) The mold is an intermediate product having a hollow portion.
(6) At least one of a male mold or a female mold is a molded product,
(7) After filling the foaming synthetic resin particles and an excess amount of water into the mold, stirring and / or shaking, and further draining the excess water, followed by heating with a non-aqueous heating means. With foam molding,
(8) The expandable synthetic resin particles are expandable polymethacrylate resin particles,
(9) The internal moisture content in the expanded synthetic resin particles containing water is 2 wt% or more and 10 wt% or less,
The present invention relates to a method for producing the foamed synthetic resin molding described above.

  2nd of this invention is related with the foaming synthetic resin molding manufactured by the manufacturing method of the said description.

In the present invention, the mold is filled with expandable synthetic resin particles and water in advance.
Preferably, in order to use the foamed synthetic resin particles containing water for foam molding, after filling in the mold, without heating by water-based heating means by steam as in normal foam molding, by non-aqueous heating means, For example, foam molding in closed molds and hollow products is possible. Therefore, in a closed system having no vapor holes, a foamed synthetic resin molded article having excellent fusing property and thus excellent strength can be obtained. Furthermore, since the foamed synthetic resin molded body sealed in a hollow product does not come into contact with air or water, it can retain excellent heat insulation and strength for a long time without worrying about water absorption. In particular, a foamed synthetic resin molded article using polymethacrylic ester resin particles is excellent in weather resistance. Therefore, if it is an ordinary foamed polystyrene resin molded article, it will deteriorate and become difficult to use in a short period of time. It can also be used outdoors.

  The present invention is a method for producing a foamed synthetic resin molded body, wherein foamable synthetic resin particles and water are filled in a mold and then subjected to foam molding by heating with a non-aqueous heating means. The expandable synthetic resin particles used in the present invention are preferably expandable synthetic resin particles obtained by pre-expanding the expandable synthetic resin particles with water vapor or the like by an ordinary method. In the present invention, even when simply referred to as expandable synthetic resin particles, it often means pre-expanded expandable synthetic resin particles.

  There is no particular limitation on the method of filling the foamable synthetic resin particles and water into the mold, and the foamable synthetic resin particles and water may be filled, or after the foamable synthetic resin particles are sprayed with water. Examples thereof include a method of filling in a mold and a method of containing foamable compatible resin particles with water. When filling the foamable synthetic resin particles and water, the water is uniformly adhered to the surface of the foamable synthetic resin particles by stirring or vibrating them, or using a combination of stirring and vibration. Is more preferable. Furthermore, in the case of filling the foamable synthetic resin particles and water, if excessive water is present in excess of the required amount after coexisting without stirring and / or shaking, It is preferable to discharge out of the system.

  Among these, foaming molding is performed by filling resin particles containing water in the foamable synthetic resin particles into a mold and then heating by a non-aqueous heating means, thereby obtaining uniform moisture dispersion. In addition, since there is no excessive excess of moisture in the system, there is little inhibition of moldability due to excess moisture, and the moisture content of the obtained molded product is not too high, and dry foamed synthetic resin molding Since a body is obtained, it is preferable. Although the amount of water to be contained in the foamable synthetic resin particles is not strictly specified, the preferable internal water content is about 2% by weight to 10% by weight, and more preferably 3-8%. It is about 3% by weight, particularly preferably about 3 to 7% by weight. Examples of the method of containing water inside include a method of containing water inside the foamable synthetic resin particles by immersing the foamed synthetic resin particles in water, but among them, the particles have a property of easily containing water, that is, It is preferable to use expandable synthetic resin particles comprising a synthetic resin having water absorption. Specific examples of the synthetic resin constituting the expandable synthetic resin particles that can be used in the present invention include a styrene resin obtained by copolymerizing a hydrophilic monomer; and a hydrophilic monomer. Examples thereof include polyolefin resins such as polymerized polyethylene and polypropylene; resins such as polymethacrylate resin and polylactic acid resin.

  Here, the hydrophilic monomer includes those obtained by removing the styrene monomer from those exemplified for the copolymerizable monofunctional unsaturated monomer described later.

  In the present invention, it is preferable to use a styrene-based resin or a polymethacrylic acid ester-based resin, and among them, the use of a polymethacrylic acid ester-based resin has an appropriate water absorption and good fusion. It is preferable because of its properties.

  Examples of the polymethacrylate resin include 70 to 100% by weight of a methyl methacrylate monomer unit and other monofunctional unsaturated copolymerizable therewith as described in JP-A-2001-233986. The weight average molecular weight obtained by polymerizing a monomer component consisting of 0 to 30% by weight of a monomer unit and 0 to 0.2 mol% of a polyfunctional monomer is 250,000 to 800,000. Examples include methyl methacrylate resin particles.

  Examples of copolymerizable monofunctional unsaturated monomers include, for example, methacrylic acid esters such as ethyl methacrylate, propyl methacrylate, butyl methacrylate, benzyl methacrylate; methyl acrylate, ethyl acrylate, propyl acrylate, Acrylic acid esters such as butyl acrylate and 2-ethylhexyl acrylate; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; acid anhydrides such as maleic anhydride and itaconic anhydride; acrylic acid 2 -Hydroxyethyl, 2-hydroxypropyl acrylate, monoglycerol acrylate, 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, hydroxyl group-containing esters such as monoglycerol methacrylate; acrylamide, methacrylamide, diacetone There is acrylamide. Nitriles include nitrogen-containing monomers such as acrylonitrile, methacrylonitrile, diacetone acrylamide and dimethylaminoethyl methacrylate; epoxy group-containing monomers such as allyl glycidyl ether, glycidyl acrylate and glycidyl methacrylate; styrene, Examples thereof include styrene monomers such as α-methylstyrene. Among these, those having a composition range of 70% by weight or more of methyl methacrylate, 0 to 10% by weight of vinyl aromatic hydrocarbon, and 0 to 30% by weight of methacrylic acid ester or acrylic acid ester other than methyl methacrylate are preferable.

  The weight average molecular weight (Mw) of the expandable polymethacrylic ester resin particles is preferably 250,000 to 800,000, and more preferably 300,000 to 600,000.

  The polymethacrylic ester resin particles are composed of the above-mentioned monofunctional unsaturated monomer, a component that becomes a polyfunctional constituent unit including a polyfunctional monomer, and, if necessary, a chain transfer agent and / or a polymerization initiator. Is obtained by polymerization. As a component which becomes a multifunctional structural unit, a multifunctional monomer has a large effect, but a multifunctional chain transfer agent, a multifunctional initiator, and a mixture thereof are listed as having a similar function. Can do.

  As a polymerization method for obtaining methacrylic ester resin particles, a known polymerization method for producing a general methacrylic ester resin can be applied. That is, suspension polymerization, bulk polymerization, and emulsion polymerization. Among them, the method of polymerizing methacrylic ester resin particles by suspension polymerization is preferable because it eliminates the pelletization step, and there is no thermal decomposition of the resin, and there are great advantages in terms of cost.

  Expandable synthetic resin particles can be obtained by incorporating the following readily volatile foaming agent into the synthetic resin particles as described above by means such as impregnation.

  Examples of readily volatile blowing agents include aliphatic hydrocarbons such as propane, butane and pentane, alicyclic hydrocarbons such as cyclobutane and cyclopentane, and fluorinated hydrocarbons such as difluoroethane and tetrafluoroethane that have zero ozone depletion potential. And carbon dioxide. These can be used alone or in combination of two or more. The content of the foaming agent is preferably 3% by weight or more and 12% by weight or less.

  As a foaming agent impregnation method, there is a method in which polymer resin particles are suspended in an aqueous medium and a foaming agent is press-impregnated. In addition, when polymer resin particles are polymerized by suspension polymerization, they may be added during the polymerization process or after the completion of the polymerization process. Furthermore, the polymer resin particles and the foaming agent may be melt-mixed using an extruder.

The internal moisture content in the foamed synthetic resin particles containing water can be measured by a known method. For example, the weight (W ₁ ) of the foamable resin particles wiped off the moisture adhering to the surface is weighed. From the difference from the weight (W ₂ ) of the resin particles after removing the volatile components in an oven at 150 ° C. for 30 minutes, the expandable resin particles before separately containing water are separated in an oven at 150 ° C. for 30 minutes. A value obtained by subtracting the total volatile component weight (W ₃ ) including the foaming agent contained in the resin particles measured by heating is defined as the internal moisture content (W ₄ ).
W ₄ (g) = W ₁ (g) −W ₂ (g) −W ₃ (g)

The internal moisture content refers to the ratio (%) of the internal moisture content to the weight of the expandable resin particles.
Internal moisture content (%) = (W ₄ / W ₁ ) × 100

  In the present invention, when the internal moisture content in the expandable synthetic resin particles is simply referred to, a numerical value when the expandable synthetic resin particles are allowed to stand for 3 minutes at a water depth of 50 mm at room temperature is used as a representative value.

  In the present invention, the non-aqueous heating means generally means means that is not steam heating generally used in the in-mold molding method, and preferably a heating method using a dry heat furnace such as an oven or microwave heating. It can be illustrated. Among these, it is preferable to perform heating with microwaves.

  The heating temperature only needs to be heated to a temperature at which the foamable synthetic resin particles foam. For example, when foamable polystyrene resin particles are used, if heating for a long time is possible, heating is performed at a temperature of about 100 ° C. or more to a short time. If the foamable polymethacrylic acid ester resin particles are used at about 150 ° C. or higher, the temperature should be about 100 ° C. or higher if long-time heating is possible to about 150 ° C. or higher if short-time heating is performed. It is preferable.

  The present invention is more effective by using a mold that does not have vapor holes when the foamable synthetic resin particles containing moisture therein are heated by a non-aqueous heating means.

  Molds that do not have steam holes are molds that are used for normal in-mold foam molding, and those that do not have steam holes, surface materials that form the appearance of products that are integrally molded with foam, etc. Can be mentioned. Examples of products formed by integrally molding a foam include, for example, intermediate products having a hollow portion, a product formed by integrally molding a foam on one side of a surface material, etc. it can. More specifically, examples of the former include sports equipment such as bats, rackets, and golf clubs, steel, wooden, and plastic furniture such as desks and chairs, and examples of the latter include a bathtub. Floor panels, wall panels, ceiling panels, refrigeration / freezer panels, refrigeration / refrigeration vehicles, aircraft panels, and the like. In these products, since the surface material constitutes the appearance of the product, when used as a mold, it is usually difficult to provide a vapor hole. In the present invention, such a surface material is directly used as a mold, filled with expandable synthetic resin particles, and heated by a non-aqueous heating means, and foamed using internal moisture contained in the particles. A foamed synthetic resin molding can be obtained by molding. Further, at least one of the male mold and the female mold may be a molded product.

  A known material can be used as the material of the mold, and in the present invention, a desired surface material can be used, and various materials can be selected depending on the heating method, purpose, and the like. Specific examples include materials such as metals, synthetic resins, glass, ceramics, wood, minerals, cloth, and paper. In the case of performing heating with microwaves, it is preferable that the material be a material that allows microwaves to pass therethrough, and examples thereof include non-metallic materials such as heat-resistant synthetic resins and ceramics. When heating by a dry heat furnace such as an oven, a heat-resistant material is preferable.

  Hereinafter, the present invention will be described in detail using examples, but the present invention is not limited to these examples.

  In addition, the evaluation in an Example evaluated as follows.

  Internal fusion: The fracture surface of the molded body is observed, and the ratio of the area where the particle surface is not exposed and the inside where the particle is broken is exposed as a percentage of the broken area. The larger the value, the better the internal fusion.

Surface elongation: Good elongation.
△ There are some problems as a product.
Evaluation (indicates overall evaluation of internal fusion and surface elongation):
◎ Very good.
○ Good.
△ There are some problems as a product.

Example 1
A pre-expanded expandable polystyrene resin particle (manufactured by Kaneka Co., Ltd., trade name Kanepal NSG, expansion ratio 25 times) is filled in an aluminum bat-shaped container having a volume of about 1 L, and the upper and lower lids are closed. After 5 minutes of immersion in water, water is poured from the gap between the lids to absorb or adhere, and then the container is lifted from the water and left for 3 minutes to remove excess water. Then, it was left still in an oven at 115 ° C. and taken out after heating for 60 minutes. After cooling with water, the container was opened and the molded body was taken out. The results are shown in Table 1.

(Example 2)
In the same container as in Example 1, instead of expandable polystyrene resin particles, pre-expanded expandable polymethacrylate resin particles (manufactured by Kaneka Corporation, trade name Kanepal AX, expansion ratio 25 times) Except that was filled, a molded body was obtained under the same conditions as in Example 1, and then taken out in the same manner. The results are shown in Table 1.

（実施例３）
実施例１と同一の容器の中に、実施例１と同一の予備発泡した発泡性ポリスチレン樹脂粒子を充填した後、容器を水中に約２０秒間浸した後、容器を取り出して、３分間放置して脱水を行い、その後、１１５℃のオーブン内に静置させて６０分加熱後に取り出し、水冷した後容器の蓋を開けて成形体を取り出した。結果を表２に示す。

(Example 3)
After filling the same pre-foamed expandable polystyrene resin particles as in Example 1 in the same container as in Example 1, the container was immersed in water for about 20 seconds, then the container was taken out and left for 3 minutes. Then, it was left in an oven at 115 ° C., taken out after heating for 60 minutes, cooled with water, then the lid of the container was opened, and the molded body was taken out. The results are shown in Table 2.

Example 4
The same operation as in Example 1 was performed by replacing the expandable polystyrene resin particles with the same pre-expanded expandable polymethacrylate resin particles as in Example 2, and the results are shown in Table 2.

(Reference example)
A comparative experiment was carried out on the amount of water absorption between the pre-expanded expandable polystyrene resin particles used in Example 1 and the pre-expanded expandable polymethacrylate resin particles used in Example 2. Each pre-expanded particle (expansion ratio 25 times, about 5 g) was put in a mesh container and allowed to stand at a room depth of about 50 mm at room temperature, and the amount of water absorption per hour was measured. For the measurement, after each immersion time, the pre-foamed particles were taken out, the surface moisture was adsorbed with a filter paper or the like, the weight was measured after 3 minutes, and the volatile matter was removed in an oven at 150 ° C. for 30 minutes. Measure the weight. Prior to this test, the total volatile content of the pre-expanded particles was measured by heating in an oven at 150 ° C. for 30 minutes, so the amount of water absorption was estimated by removing from the weight after water absorption. The results are shown in Table 3.

Claims (11)

  A method for producing a foamed synthetic resin molded article, comprising filling foamable synthetic foamed resin particles and water in a mold and then performing foam molding by heating with a non-aqueous heating means.   The method for producing a foamed synthetic resin molded article according to claim 1, wherein the foamed synthetic resin particles containing water are filled in a mold and then heated by a non-aqueous heating means.   The manufacturing method of the foaming synthetic resin molding of Claim 1 or 2 formed by using the shaping | molding die which does not have a vapor hole.   The method for producing a foamed synthetic resin molded article according to any one of claims 1 to 3, wherein the non-aqueous heating means is a microwave.   The method for producing a foamed synthetic resin molded body according to claim 4, wherein the mold is made of a nonmetallic material.   The method for producing a foamed synthetic resin molded body according to any one of claims 1 to 5, wherein the mold is an intermediate product having a hollow portion.   The method for producing a foamed synthetic resin molded body according to any one of claims 1 to 6, wherein at least one of a male mold or a female mold is a molded product.   After filling the foamable synthetic resin particles and an excess amount of water into the mold, stirring and / or shaking, and further discharging the excess water, followed by heating by non-aqueous heating means The manufacturing method of the foaming synthetic resin molding as described in any one of Claims 1-7.   The method for producing a foamed synthetic resin molded article according to any one of claims 1 to 8, wherein the foamable synthetic resin particles are foamable polymethacrylic ester resin particles.   The foamed synthetic resin molded article according to any one of claims 2 to 9, wherein the internal moisture content in the foamed synthetic resin particles containing water is 2 wt% or more and 10 wt% or less. Method.   The foaming synthetic resin molding manufactured by the manufacturing method of any one of Claims 1-10.