JPS60235850A - Foamed molding of polyolefin resin and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain the titled molding of prefoamed particles in a mold, which is light and has excellent heat insulating properties, etc., by bonding dispersed polyolefin fibers and polyolefin resin foam with a low-melting polyolefin. CONSTITUTION:Composite fibers (A) consisting of a core part, having a fineness of 2-50de, comprising a polyolefin resin (a) which does not soften at the molding temperature for the prefoamed particles to be molded and a sheath part comprising a polyolefin resin (b) which melts at the molding temperature for the component (a) and has a melting point by at least 10 deg.C lower than that of component (a); of a length of 2-30mm. after having been stretched to increase the length 2-10 times to give an extensibilty of 20-150%; and prefoamed paticles of polyolefin resin for molding (B) are mixed. This mixture is put in a metal mold and heated to cause refoaming and fusion-bonding of the particles of component B to obtain the titled foamed molding, in which the foamed segments of component B 1a-1f are fusion-bonded to each other, forming macroscopically a uniform foamed molding, and component (a) 2 is bonded to component B 1a-1f by way of component (b) 3 as a bonding-agent layer.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides polyolefin systems 1 with improved physical properties.
it (related to fat foam molded articles and methods for producing the same).

High-magnification foam molded products made of thermoplastic composites and resins take advantage of their excellent lightness, heat insulation, and cushioning properties, and can be used as heat insulating materials, slow-poring materials, and i? It is widely used for bulletin boards, bedding, building materials, packaging materials, etc. However, by containing a large amount of air bubbles, the higher the expansion ratio, the lower the bending strength and tear strength, and the more brittle the foam tends to be. Such a tendency is particularly remarkable in the case of a foam molded article manufactured by in-mold molding of pre-expanded particles of raw resin. This is because, unlike resin extrusion foam molding, when pre-foamed particles are used, the strength of the fusion between the pre-expanded particles governs the strength of the molded product, and therefore it is not as strong as expected from the physical properties of the foam itself. 6 Among foamed molded products, those made of polyolefin resin are more resistant to bending than the most commonly used polystyrene-based products, but on the other hand, in many applications, they are difficult to maintain rigidity. It has the disadvantage of being insufficient. Therefore, conventional in-mold foam molded articles of synthetic resin cannot be used in places where large bending stress is applied.

An object of the present invention is to eliminate the above-mentioned drawbacks of a foam molded product produced by in-mold molding of pre-expanded particles.

The present invention, which has succeeded in achieving the above objects and providing a composite rk with high physical properties, a resin foam molded product, and a method for producing the same, has a polyolefin resin foam containing polyolefin fibers in a dispersed state, and a polyolefin resin foam containing a polyolefin resin foam. An invention of a polyolefin resin foam molded article characterized in that the body and polyolefin fibers are bonded together by a low melting point polyolefin, and a polyolefin resin foam molded article is filled with pre-expanded polyolefin resin particles into a mold and heated, and the pre-expanded article is heated. In producing a polyolefin resin foam molded product by molding the particles by causing re-foaming and interparticle fusion, a core made of a polyolefin resin that does not soften at the molding temperature of the pre-expanded particles and the polyolefin resin are used. Invention of a method for producing a polyolefin resin foam molded article, which comprises molding pre-expanded particles mixed with a core-sheath composite fiber having a sheath made of a low melting point polyolefin resin that melts at the molding temperature of the resin. Consists of two inventions.

FIG. 1 is a partially enlarged sectional view of a polyolefin resin foam molded article according to the present invention. The polyolefin foams 1a to 1f are each formed from separate pre-expanded particles, but are fused together to form a macroscopically uniform foamed molded product. Polyolefin fiber 2 is
The thin film-like low melting point polyolefin 3 is used as an adhesive layer to adhere to the polyolefin resin foams 18 to 1f. In the polyolefin resin foam molded article of the present invention having such a structure, the bond between the pre-expanded particles is reinforced with polyolefin fibers, and the polyolefin resin foam molded article of the present invention can be formed by simply mixing the polyolefin fibers and the polyolefin resin pre-expanded particles. Unlike conventional molded polyolefin resin foams, polyolefin fibers and polyolefin resin foams are firmly bonded by an adhesive layer made of low melting point polyolefin, so they exhibit far superior physical properties than conventional polyolefin resin foam moldings. It is something. The polyolefin resin foam molded article of the present invention has particularly excellent bending strength, tear strength, resistance to local compression, and the like.

Polyolefin system 11jJI according to the invention? The l'f foam molded product also has the ability to not generate harsh high-frequency sounds even when its smooth surface is rubbed against the smooth surface of other foam molded products of the same or different type, metal products, or composite products (oil products, etc.). It has this feature.

The above-mentioned effect is particularly remarkable when using stretched short polyolefin fibers (2 to 30 m in length) with low elongation and high strength.
It is a foamed molded product reinforced with If the polyolefin fibers are too short, the effect of adding them will be small; on the other hand, if they are too long, they will become tangled during the manufacturing process, making it difficult to mix uniformly, resulting in poor efficiency.

Suitable materials for the polyolefin fibers are polyolefins having a relatively high softening point that do not soften at the molding temperature of the pre-expanded particles, such as polypropylene, polybutene, high-density polyethylene, ultra-high molecular weight polyethylene, polypentene-1, and the like. Fibers other than polyolefin fibers, both organic and inorganic fibers, have poor affinity with polyolefin resin foams, so even if an adhesive layer is provided, there will be no adverse effect on the properties of polyolefin resin foam moldings. The reinforcing polyolefin fibers, which do not exhibit a large reinforcing effect, may be cut from multifilament yarns made by bonding single yarns together.

The polyolefin fibers do not need to be uniformly dispersed throughout the foam molded article, and may be present at a higher rate near the surface of the molded article than in the core, for example.

The low melting point polyolefin constituting the adhesive layer is a polyolefin having a melting point lower than at least the melting point of the material resin of the reinforcing polyolefin fiber (preferably a melting point lower by 10°C or more). Although this requirement has nothing to do with the physical properties of the polyolefin resin foam molding, it is virtually impossible to produce a combination of melting points that are inversely related to each other. In the case where the reinforcing polyolefin fibers are polypropylene fibers with a melting point of 165°C and the polyolefin constituting the foam is high-density polyethylene with a melting point of 132°C, examples of usable low-melting polyolefins are:
Ethylene-vinyl acetate copolymer (melting point 92℃), low density polyethylene (melting point 108℃), medium density polyethylene (melting point 108℃)
(melting point: 122°C), high-density polyethylene (melting point: 132°C)
)and so on.

Although the polyolefin resin constituting the polyolefin resin foam molded article of the present invention is not particularly limited,
Particularly preferred in relation to the purpose of the present invention are polyethylene, polypropylene, ethylene-propylene co-11,
Examples include those obtained by crosslinking and modifying ethylene-vinyl acetate copolymers, 1,2-polybutadiene, graft copolymers of polyolefin and polystyrene, and mixtures of polyolefin and polystyrene.

Next, a method for producing the polyolefin resin foam molded article according to the production method of the present invention will be explained.

In the manufacturing method of the present invention, first, a core comprising a core made of a polyolefin resin that does not soften at the molding temperature of the pre-expanded particles to be molded and a sheath made of a polyolefin resin that melts at the molding temperature of the polyolefin resin. Prepare a sheath type (also called sheath type) composite fiber. The core portion serves as the reinforcing polyolefin fiber in the polyolefin resin foam molded product of the present invention, and the sheath portion serves as the adhesive layer between the polyolefin fiber and the foam in the same foam molded product. These materials are selected from among the materials already mentioned for the polyolefin fibers and the adhesive layer.6 The method for producing core-sheath composite fibers from the selected materials is arbitrary, and the core arrangement is eccentric. There is no problem. The thickness of the fiber is
The core is about 2 to 50 denier, and the weight ratio of the core to the sheath is:
The former is 10, while the latter is 5 to 20. After spinning, the composite fiber is preferably stretched 2 to 10 times to have an elongation of 20 to 150% and a high strength, and then cut into lengths of 2 to 30,111 mm.

The obtained core-sheath composite fiber is mixed or mixed with pre-expanded polyolefin resin particles for molding produced by a conventional method and filled into a mold for molding. Thereafter, the molding process by heating to cause re-foaming of the -F@expanded particles and interparticle fusion may be carried out in the same manner as in the production of conventional polyolefin resin foam moldings.Pre-expanded particles In the process of heating and re-foaming, the sheath part of the core-sheath type composite fiber melts, and the core part does not melt or soften. The sheath portion of the core-sheath type composite fiber sandwiched between the core and sheath type composite fibers melts and at the same time acts as an adhesive between the core polyolefin and the foam, forming an adhesive structure between the foam and the polyolefin fiber as described in ii+7. Ru.

The polyolefin resin foam molded article of the present invention can be produced by a method other than Nisha's manufacturing method, such as a method using a side-by-side composite fiber of polyolefins with different melting points instead of the core-sheath composite fiber in the above manufacturing method, or a method using a fiber made by combining polyolefins with different melting points side-by-side, It can also be produced by a method using polyolefin fibers coated with an adhesive made of polyolefin, but according to the production method of the present invention, the polyolefin fibers are completely covered with the low melting point polyolefin that becomes the adhesive layer. The effect of adding polyolefin fibers is to ensure that adhesion is achieved, and when the sheath is made sufficiently thick, it becomes a kind of heat insulating layer that prevents or suppresses the molecular orientation of the core polyolefin fibers from collapsing due to temperature rise. is the most certain and obvious.

The polyolefin resin foam molded product according to the present invention takes advantage of the above-mentioned features, and can be used not only in fields where polyolefin resin foam molded products and polystyrene resin foam molded products were conventionally used, but also in fields that were previously difficult to use. field,
For example, it can be widely used in bedding, kungjong, furniture, and various other durable consumer goods. Traditionally, polyurethane foam was mainly used in these fields, but
The present invention makes it possible to replace this with a cheaper polyolefin resin foam molded article.

The present invention will be explained below with reference to Examples.

Example 1 High-density polyethylene with a melting point of 132° C. and a density of 0.95887 cm was crosslinked by a conventional method to obtain crosslinked polyethylene particles with a gel fraction of 18%, which were pre-foamed by a conventional method to obtain an expansion ratio of 52. On the other hand, the following core-sheath type composite fiber A11. (core part 4 Against the sheath part 6
Two types were manufactured with a weight ratio of .

Composite fiber A: Stretching ratio 3 times, fineness 6d, fiber length 15 Composite fiber B: Stretching ratio 6x 1wL degree 3 (1, fiber length 15I
The above pre-expanded particles were placed in pressurized air to a temperature of 1.4 g/e.
IO:(((:)) and the above composite fibers of <1fiL were mixed to form a 300mm x 300m
IIIX Filled in a 50mm mold and heated to 135℃
was blown into shape. For comparison, molding was carried out in the same manner except that composite fibers were not mixed. The results are shown in Table 1.

Table 1 Example] Fork pile? ----Le Example- Raw material blending ratio (weight ratio) Pre-expanded particles 5 7 10 Composite fiber A 5 0 (+ Composite JJiiB 0 3 0 Tensile strength (Kg/c+e2) 4.4 3.1 2.
9 Tear strength” (Kg/cm) 3.6 2.2 1.6
Compression hardness” (K8/cm2) 0.6 0.6 0.5
Local IL fat, breaking load'; (to H) 64.4 55.
(126.5 bending strength (K6.□cm:)” 3.5
3.4 2.2"JISK6"767 L The center of the plate-shaped sample with a thickness of 25IIIo is the diameter 1)
, with a cylinder of 8 cm I Q l) mm/m
The load at which the sample breaks when compressed at a compression speed of in.

” 2 (For a rod-shaped sample of 1 am
Measured at /min.

[Brief explanation of drawings]

FIG. 1 is a partially enlarged sectional view of a polyolefin resin foam molded article according to the present invention. 1: Polyolefin resin foam 2: Polyolefin fiber 3: Low melting point polyolefin agent Patent attorney Itaben-Kanzai A diagram

Claims (4)

[Claims] (1) Polyolefin resin foam is polyolefin w
1. A polyolefin resin foam molded article formed by in-mold molding of pre-expanded particles, which contains L fibers in a dispersed state, and wherein the polyolefin resin foam and the polyolefin fibers are bonded by a low melting point polyolefin. (2) The polyolefin resin foam molded article according to claim 1, wherein the polyolefin fiber is polypropylene fiber and the low melting point polyolefin is polyethylene. (3) Filling a mold with pre-expanded polyolefin resin particles and heating them to cause re-foaming of the pre-expanded particles and interparticle fusion to produce a polyolefin resin foam molded article. A core-sheath composite fiber having a core made of a polyolefin resin that does not soften at the molding temperature of the pre-expanded particles and a sheath made of a low melting point polyolefin resin that melts at the molding temperature of the polyolefin resin is mixed. 1. A method for producing a polyolefin resin foam molded article, which comprises molding pre-expanded particles. (4) The manufacturing method according to claim 3, which uses a core-sheath type composite fiber having a core 8 made of polypropylene and a core made of polyethylene.