WO2001092387A1 - Molded object comprising resin foam and solid particles and process for producing the same - Google Patents

Abstract

A lightweight heat-insulating molded object containing solid particles reclaimed from a plastic waste, etc. It comprises resin foam particles and the solid particles, wherein all the particles are irregularly mixed and bonded to one another through an adhesive layer. This molded object is produced by heating in a mold a mixture of solid particles whose surface has been coated with a precursor for a thermosetting resin and pre-expanded expandable resin particles whose surface has been likewise coated with a precursor for the thermosetting resin to thereby expand the pre-expanded expandable resin particles.

Description

 Description: Molded article comprising resin foam and solid particles and method for producing the same

 The present invention relates to a molded article mainly composed of a resin foam suitable for a heat insulating material, a cushioning material, a packaging case, a float, and the like, and a method for producing the same. Background art

 Conventionally, in order to reuse plastic waste material, when the waste material is made of a thermoplastic resin, a method of melting and molding the waste material (material recycling) has been adopted. However, according to this method, if a different material is mixed, the mechanical strength of the obtained molded body often decreases. Therefore, measures have been taken to prevent deterioration of physical properties by mixing a compatibilizer. However, since compatibilizers are generally expensive, it is necessary to separate resins in order to perform material recycling. In addition, when a resin having a hydrolyzability such as a polyester resin and a polycarbonate resin is not sufficiently dried to have a residual water content of about 0.02% or less, hydrolysis is accelerated due to a high temperature during molding. The molecular weight is greatly reduced, and a molded article having a desired mechanical strength cannot be obtained. Therefore, extra energy is required for drying.

 On the other hand, thermosetting resin does not melt and cannot be molded into any shape. Rubber materials other than thermoplastic elastomers are almost crosslinked, that is, the crosslinked rubber material is a thermosetting resin, and material recycling is not possible.

The resin foam is usually made by foaming resin foam particles containing a foaming agent to a desired expansion ratio in advance, filling the prefoamed body into a mold, and heating the foam. Obtained by foaming. This resin foam only added a coloring agent and the like in addition to the foam component, and was not mixed with other resin materials or rubber materials to be integrally molded. If the resin foam can successfully contain other materials, new functions can be added.

 In view of the above, the present invention effectively recycles plastic waste materials made of not only thermoplastic resins but also thermosetting resins, and plastic waste materials mixed with different kinds of resins. It aims to provide a way to use it.

 Another object of the present invention is to provide a lightweight molded article made of recycled plastic waste.

 Still another object of the present invention is to provide a new foam that includes not only plastics but also inorganic substances. Disclosure of the invention

 As a result of repeated studies in consideration of the above-mentioned problems, the present inventor has coated various solid particles such as plastic waste materials and foamable resin particles with an adhesive, mixed them, and placed them in a mold. Thus, a molded product in which the solid particles and the resin foam were bonded by an adhesive was successfully obtained.

 That is, the molded article of the present invention is characterized in that the resin foam particles and the solid particles are mixed irregularly and are bonded by the adhesive layer. In the present invention, a mixture of solid particles whose surface is coated with a thermosetting resin precursor and pre-expanded foamable resin particles whose surface is similarly coated with a thermosetting resin precursor is prepared. And a foaming step of heating the mixture in a mold to fully expand the pre-expanded expandable resin particles.

According to the present invention, a reinforcing member is set in a mold prior to the foaming step. And a method for producing a molded article that obtains a molded article including the reinforcing member by a foaming step. BRIEF DESCRIPTION OF THE FIGURES

 FIG. 1 is an enlarged sectional view for explaining a molding step of a molded article according to an embodiment of the present invention.

 FIG. 2 is a cutaway perspective view of a main part of a molded body according to another embodiment of the present invention.

 FIG. 3 is a perspective view of a molded body according to still another embodiment of the present invention, in which main parts are cut away. BEST MODE FOR CARRYING OUT THE INVENTION

 As described above, the present invention relates to a method for coating solid particles and resin foam by coating and mixing the expandable resin particles and solid particles with an adhesive, and foaming the resulting mixture in a mold. Is to obtain a molded article bonded by an adhesive.

 In a preferred embodiment of the present invention, the pre-expanded foamable resin particles and the foamed resin particles after the firing have a one-to-one correspondence, and therefore, the pre-expanded foamable resin particles filled in the mold and The mixture of the solid particles is formed into a molded body in which the expanding resin particles enter the gaps between the solid particles by the main foaming, and the solid particles adhere to each other by the expansion force, and are firmly bonded by the curing of the adhesive layer. Becomes

Examples of the material of the solid particles include various resin materials, rubber materials, organic materials such as paper (for example, waste paper) and wood, or granular inorganic materials such as shirasu balloons, pearlite, talc, kaolin, recycled glass, and ceramics. Various types such as crushed particles of cousin concrete, small pebbles that exist in nature And inorganic materials and organic materials. These may be used alone or in combination of two or more. These solid particles can be appropriately blended with the foaming resin according to the desired properties such as heat insulation and mechanical strength of the molded article.

 Since the method for producing a molded article according to the present invention can be applied irrespective of the material of the solid particles, not only the virgin (new) material of the above-mentioned materials but also a material obtained by appropriately treating waste materials is used. Is also suitable. For example, plastic recycling can be performed for thermoplastic resin that is melted by heat, but the mechanical strength of the resulting molded article often decreases when different types of materials are mixed. Therefore, conventionally, measures have been taken to prevent deterioration in physical properties by mixing a compatibilizer. However, since the compatibilizer is expensive, it is necessary to separate the resin when recycling the raw materials. On the other hand, according to the present invention, there is a great merit that such a compatibilizer is not required.

 As a material of the resin foam particles, for example, a thermoplastic resin such as polystyrene, polyvinyl chloride, and ABS resin is suitably used.

 In producing the molded article of the present invention, a resol-type phenol resin precursor is inexpensive and has a low curing temperature and is most suitable as an adhesive layer covering the surfaces of the expandable resin particles and the solid particles. In particular, in order to obtain a molded article requiring heat resistance, it is preferable to use a precursor of an imido-based resin. When a resol-type phenol resin precursor is used for the adhesive layer, about 120 ° C. As the curing proceeds, molding can be performed at a temperature lower than the melting temperature of general thermoplastic resin during injection molding (200 ° C or higher even with polystyrene having a relatively low melting temperature), and the energy saving effect is large.

It is preferable to add a curing accelerator to the adhesive layer to shorten the curing time. When using a resol type phenolic resin precursor for the adhesive layer. It is preferable to use phenolsulfonic acid or toluenesulfonic acid as the curing accelerator.

 A flame retardant such as a boron-based inorganic compound, aluminum hydroxide, or magnesium hydroxide can be added to the adhesive layer. Addition of these flame retardants can impart flame retardancy to the obtained molded article. The flame retardant effect of boron-based inorganic compounds is considered as follows. That is, the boron-based inorganic compound contained in the adhesive layer, for example, boric acid, is heated by combustion and changes to a glassy substance, and the combustible substance inside is shut off from the air by this glassy substance, thereby As a result, a flame retardant effect is exhibited. However, when the solid particles are flammable, the amount of the adhesive layer covering the flammable substance is small in quantity with respect to the weight of the flammable substance, so that the flame retardant effect is hardly exhibited. However, when the solid particles are a resin foam, for example, a crushed foam of a foamed polystyrene foamed several tens of times, the proportion of the adhesive layer imparting flame retardancy to the weight of the solid particles is large. Therefore, a molded article having a large flame retardant effect can be obtained. In addition, resole-type phenol resins, polyimide resins, melamine resins, and the like have self-digestibility, and therefore, it is preferable to use them as the adhesive layer. In the case of non-flame-retardant resin in which solid particles are hard to impart flame retardancy, if a flame retardant such as boric acid is kneaded in advance before forming the particles, great flame retardancy can be imparted, And the shape collapse at the time of flame contact becomes small.

The expandable resin particles used in the present invention are preferably pre-expanded. The prefoamed particles have a foaming ratio of 10 to 80 due to the prefoaming, and the expansion ratio due to the main foaming is such that the bonding between the foamed particles and the solid particles by the adhesive is performed. It is preferably from 5 to 15% so as to be good. The size of the prefoamed particles is preferably 2 to 4 mm in consideration of the strength and heat insulation of the obtained molded article. '' On the other hand, solid particles are particular about shapes such as pellets, crushed materials, and granulated materials. However, in order to increase the packing density of the solid particles and the pre-expanded expandable resin particles, and to increase the mechanical strength of the obtained molded product, the average particle size is desirably 1 to 5 mm. However, those exceeding these ranges may be mixed to some extent, and it is not necessary to make the sizes and shapes uniform. Rather, particles having different sizes may have better packing properties.

 As described above, when pre-expanded expandable resin particles having an average particle diameter of 2 to 4 mm and an expansion ratio of 5 to 15% due to main expansion and solid particles having an average particle diameter of 1 to 5 mm are used, adhesion is performed. The thickness of the layer is preferably 50 to 100 // m. Depending on the type of adhesive, if the thickness of the adhesive layer covering the particles is too small, the adhesive strength will be insufficient.If it is too thick, the proportion of the adhesive shown on the molded body will increase, and the molded body will become heavier. The cost is high.

In order to obtain a molded product having high mechanical strength, especially rigidity, a reinforcing member such as a paper, plastic or metal mesh, a lattice, a honeycomb structure, and a reinforced body is incorporated into the mold. as it is Degiru _£ reinforcement integrally molded with the particles, it may be added glass fibers, carbon fibers, synthetic resin fibers, natural resin fibers. By adding these reinforcing materials, it is possible to improve the mechanical strength such as the bending elastic modulus and impact resistance of the obtained molded article. <The expandable resin is a thermoplastic resin, and the solid particles are pellets of the resin material. (G) A crushed product, and a molded article having high mechanical strength can be obtained by using the adhesive layer as a precursor of a thermosetting resin such as a resol-type phenol resin or a melamine resin. Regardless of whether the solid particles are a mixture of resin materials or a thermosetting resin, a molded product having high mechanical strength can be obtained as long as it can be crushed to some extent. The compact obtained by the method of the present invention can be recycled many times by finely crushing and repeating the same production steps.

A resol type phenol resin precursor (hereinafter simply referred to as resol The method for obtaining the molded article of the present invention will be described. First, after mixing the solid particles and the pre-expanded foamable resin particles (resin particles containing a foaming agent and pre-expanded at a predetermined magnification) which are pre-expanded at a predetermined ratio, at a predetermined ratio, A predetermined amount of liquid uncured resol is added, and the surfaces of the solid particles and the expandable resin particles are uniformly coated with the uncured resol while stirring. A predetermined amount of a mixture of pre-expanded expandable resin particles coated with a resin as well as solid particles coated with a resin is filled in a mold, and the expandable resin particles are fully expanded. . The pre-expanded resin particles expand due to the volume expansion of the pre-expanded resin particles during the main expansion and the thermal expansion of the air bubbles contained in the pre-expanded resin particles, resulting in solid particles and expanded resin foam particles. At the same time, the curing reaction of the resols coated on both surfaces proceeds, and the two adhere firmly to each other, so that a molded article having high mechanical strength can be obtained.

 When removing the molded body from the mold, it is necessary to lower the mold temperature until the foamed resin of the molded body hardens to a certain extent (approximately 60 in the case of foamed polystyrene). If a flame retardant is added, the resulting molded article can be imparted with flame retardancy.

 Hereinafter, a specific example will be described.

FIG. 1 (b) schematically shows a cross-sectional structure of a molded article 1 according to the present invention. The molded article 1 is constituted by using a crushed product of polystyrene as the solid particles 2, expanded polystyrene as the resin foam particles 3, and a resin as an adhesive layer 4 for bonding the both. Solid particles include general-purpose resins such as polyethylene, polypropylene, ABS resin, and polyvinyl chloride in addition to polystyrene, nylon, polycarbonate, modified phenylene ether, polybutylene terephthalate, and glass fiber reinforced polyethylene. It can be widely applied to engineering plastics such as lenterephthalate and polyphenylene sulfide, as well as thermosetting resins such as phenolic resin, epoxy resin and unsaturated polyester resin.

 In particular, a crushed foam such as styrene foam can be used as the solid particles, and in this case, it can be reused as a material having a large heat insulating effect. In addition, when a heat-reduced volume of a foam is used, molded articles having different heat insulating properties can be obtained depending on the volume reduction rate (the larger the volume reduction rate, the smaller the number of remaining air bubbles). In this case, the higher the volume reduction rate, the lower the heat insulating properties of the obtained molded body, but the greater the mechanical strength, and the higher the strength of the molded body, the more it can be nailed. In particular, although it has been conventionally difficult to recycle urethane foam, the method according to the present invention enables material recycling.

 If the rubber material is crushed, it can be used as solid particles, for example, natural rubber, SBR, NBR, chloroprene rubber and the like can be used. Further, thermoplastic elastomers such as polystyrene, polyurethane, and polyester can also be applied. By using these materials, it is possible to obtain a light-weight and elastic molded body having heat insulation properties.

 Next, a manufacturing process of a molded body for integrating the solid particles 2 and the resin foam particles 3 will be described with reference to FIG.

To a mixture obtained by mixing particles 2 obtained by crushing polysterene and pre-expanded polystyrene 3a at a fixed ratio, a liquid resin to be used as an uncured adhesive layer 4a is mixed while being mixed, and mixed on the surfaces of both. Coat resols tightly. Thus, a mixture of the crushed polystyrene as the particles 2 coated with the resol and the pre-expanded expandable resin particles 3a coated with the resole is prepared. Figure 1 (a) schematically shows this state. Show. Next, this mixture is charged into a mold, and heated at 120 ° C. for several minutes to completely foam. As shown in FIG. 1 (b), the foamed polystyrene particles 3 and the crushed resin particles 2 adhere to each other through the respective adhesive layers 4 due to the expansion of the pre-expanded polystyrene due to the main foaming. The resol coated on the surface is cured, and both are firmly adhered to each other, so that a molded body having high mechanical strength can be obtained. In the case of resol, about 2 parts by weight of phenolsulfonic acid is added as a curing accelerator to 100 parts by weight of resol.

 The pre-expansion ratio of the pre-expanded expandable resin particles 3a to be used may be selected in the range of 10 to 80 times depending on the strength and heat insulation of the molded article according to the purpose of use. The mixing ratio of the solid particles 2 and the pre-expanded expandable resin particles 3a is such that the volume ratio of the solid particles 2 is 1 and the pre-expanded expandable resin particles 3a has a styrene foam of 1 or more. Is desirable. Pre-expanded resin particles Since the specific gravity of expanded polystyrene as 3a is extremely small, the mechanical strength is high only by using pre-expanded expanded polystyrene weighing 1/10 or less of the resin amount of solid particles 2 to be used. A molded article is obtained.

 FIGS. 2 and 3 show the molded bodies 11 and 21 obtained in the same manner as above, respectively, after setting the honeycomb structure 13 and the lattice body 23 as reinforcing members in the mold. . In these figures, layers 12 and 22 represent layers in which solid particles and foam particles are joined by an adhesive layer. Since the reinforcing material forms the skeleton of the molded body as a reinforcing member, a molded body having high mechanical strength, particularly high bending strength, can be obtained. Example 1

A 1: 1 ratio of crushed polystyrene (average particle size: about 5 mm) and pre-expanded styrene (average particle size: about 3.5 mm) foamed about 50 times by volume To obtain a mixture. Thereafter, 3 parts by weight of a resole having a molecular weight of about 200 was blended with 100 parts by weight of the mixture, and the mixture was sufficiently stirred so that the resole was applied to the surfaces of the particles of the polystyrene crushed material and the polystyrene foam of the pre-expanded particles. Coated. Next, the mixture containing the resin was filled in a mold and subjected to main foaming at 120 ° C. for 3 minutes to obtain a plate-shaped molded product of 230 × 230 × 20 mm. . The properties of the obtained molded body were as follows, density: 0.075 kgZcm ³

Pressure strength: 4 kg / cm ²

Flexural strength: 5.2 kg / cm ² Example 2

 Using a reinforcing member made of paper having a thickness of lmm, a honeycomb-shaped structure having a side of the honeycomb of 20 mm and a height of 15 mm, using the same materials and manufacturing conditions as in Example 1 as shown in FIG. A molded body having a thickness of 15 mm was produced. In addition, a molded body as shown in Fig. 3 was produced using a reinforcing member in which polypropylene round bars having a diameter of 2 mm were fused in a grid pattern at 50 mm intervals. The mechanical strength of these compacts is shown below.

 82 cam structure built-in molding

Density: 0.1 2 kg / cm ³

Pressure strength: 7.2 kg / cm ²

Flexural strength: 10 kg cm ²

 Cross-shaped rebar embedded molded body

Density: 0.1 l O k gZcm ³

Pressure strength: 4.5 kg / cm ²

Bending strength: 6. 7 kg / cm ²

In the above example, crushed resin was used alone as solid particles. A compound consisting of a plurality of organic or inorganic raw materials can be appropriately compounded so as to obtain the desired properties of the molded article.

 Since the molded article of the present invention contains a resin foam such as styrene foam, it is lightweight, has heat insulating properties, and has high mechanical strength. Further, by changing the type and the mixing ratio of the solid particles, the resin foam, and the material of the adhesive layer, molded articles having various characteristics can be obtained. Therefore, the present invention can be expected to have various applications in many fields.

 The molded article according to the present invention can have various shapes according to the purpose of use, and examples thereof include a flat plate, a box, a tray, a tube, and a sphere. As the use of the molded article of the present invention, there are typically the following uses.

 Building materials: Insulation materials for walls, floors, ceilings, etc.

 Lightweight boards: panels, fittings, partitions, etc.

 Insulation structure for various applications: Insulation material for cold insulation and heat insulation equipment Possibility of industrial use

 The molded article of the present invention is obtained by joining solid particles such as an inorganic substance or an organic substance and a resin foam with an adhesive layer having both surfaces coated. Therefore, not only virgin materials but also plastic waste materials such as rubber materials, paper pulp, wood chips, crushed stone particles, ceramic particles, and zeolite can be used as solid material particles. The material that has been crushed to a particle size of can be recycled and used. In addition, since the obtained molded article is mostly constituted by a porous foam, it is lightweight, inexpensive, and has excellent heat insulating properties and mechanical strength.

Claims

The scope of the claims 1. A molded article characterized in that resin foam particles and solid particles are mixed irregularly and bonded by an adhesive layer.  2. The molded article according to claim 1, wherein the resin foam particles are made of a thermoplastic resin.  3. The molded article according to claim 1, wherein the adhesive layer is made of a thermosetting resin ( 4. The molded article according to claim 1, wherein the adhesive layer contains a flame retardant.  5. preparing a mixture of solid particles whose surface is coated with a thermosetting resin precursor and pre-expanded expandable resin particles whose surface is also coated with a thermosetting resin precursor, and A method for producing a molded article, comprising a foaming step of heating the mixture in a mold to fully foam the pre-foamed foamable resin particles.  6. The method according to claim 5, further comprising a step of setting a reinforcing member in the mold prior to the foaming step, wherein a molded body including the reinforcing member is obtained by the foaming step. A method for producing a molded article.  7. The method for producing a molded article according to claim 5, wherein the adhesive contains a flame retardant.