Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-03-30
2001-10-09
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S138000
Reexamination Certificate
active
06300386
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to expandable synthetic resin compositions for use in the manufacture of synthetic resin foams, synthetic resin foams and methods for manufacturing synthetic resin foams, and more particularly to expandable synthetic resin compositions capable of providing foams that exhibit excellent heat distortion resistance and mechanical strength, such synthetic resin foams and methods for manufacturing the same.
PRIOR ART
Thermoplastic foams have come into widespread use as cushioning materials, heat insulation, electrical insulating materials and the others.
However, these conventional thermoplastic foams have not been completely satisfactory in their performances, as in uses where higher degrees of heat distortion resistance and mechanical strength are required. In view thereof, various methods have been proposed which include dispersing reinforcing fibers, e.g., glass fibers in a foam, and laminating a reinforcing member on a foam surface for bonding thereof.
In Japanese Patent Laying-Open No. Hei 4-110219, for example, a method is disclosed which extrudes a foam containing a dispersion of reinforcing material such as glass fibers. This method however performs foam extrusion while rigid and straight reinforcing fibers, such as glass fibers, are under dispersion. Accordingly, those fibers readily break foam cells to prevent production of foams that exhibit high expansion ratios. Also, fiber breakage caused within an extruder or die results in problematic failure to impart sufficient reinforcing effect.
In addition, those foams obtained by using the above method have imparted reinforcement thereto by incorporating reinforcing fibers such as glass fibers. Due to the fiber breakage, the attempts to recover such foams for recycling purposes nearly failed. The difficulty in reusing foam scraps forced disposal thereof.
On the other hand, Japanese Patent No. 2,503,109 discloses a method which reinforces a foam by compressively heat-bonding the form at its surfaces to a cloth. The cloth is comprised of conjugate fibers and/or conjugate yarns respectively containing adhesive and reinforcing components. Although this method achieves such effects as imparting increased rigidity to the plate-form foam and preventing the foam from flying apart when fractured by impact, the foam itself increases in weight, and the strength of a foam layer per se remains unchanged.
Japanese Patent Laying-Open Nos. Hei 3-179,040 and 3-179,042 respectively disclose foam molding of liquid crystalline polymers, instead of thermoplastic resins, which is capable of producing molded foams having increased mechanical strength. However, foaming liquid crystalline polymers alone results in production of foams having expansion ratios of no more than 2. Consequently, beneficial properties of foams, i.e., lightweight and heat insulating properties can not be imparted to the resulting, molded foam products.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an expandable synthetic resin composition capable of producing foams which are excellent in both heat distortion resistance and mechanical strength and also exhibit higher expansion ratios, such synthetic resin foams and methods for manufacturing the same.
A first invention of the present application is the aforementioned expandable synthetic resin composition which is characterized as including a thermoplastic resin, a liquid crystal resin (or polymer) and a heat-decomposable foaming agent.
The expandable synthetic resin composition preferably contains 0.1-60 parts by weight of the liquid crystal resin, and 40-99.9 parts by weight of the thermoplastic resin.
The expandable synthetic resin composition further contains the heat-decomposable foaming agent in an amount of 0.5-30 parts by weight, based on 100 parts by weight of the aforementioned thermoplastic and liquid crystal resins.
In the expandable synthetic resin composition, it is preferred that the aforementioned thermoplastic resin consists at least partly of a crosslinking resin.
It is further preferred that the aforementioned liquid crystal resin is fibrillated.
A second invention of the present application is a synthetic resin foam characterized as including a thermoplastic resin and a liquid crystal resin dispersed in the thermoplastic resin, and as having been expanded to an expansion ratio of 1.1-50.
For the synthetic resin foam in accordance with the present invention, 0.1-60 parts by weight of the liquid crystal resin is mixed with 40-99.9 parts by weight of the aforementioned thermoplastic resin for dispersion of the liquid crystal resin therein.
It is also preferred that the above-stated liquid crystal resin is at least partly fibrillated.
In the synthetic resin foam in accordance with the present invention, the aforementioned thermoplastic resin is comprised preferably of a polyolefin resin, more preferably of a combination of a non-crosslinking polyolefin resin and a crosslinking polyolefin resin.
A third invention of the present application is a method for manufacturing a synthetic resin foam characterized as including the steps which follow. In a first step, a mixture of a liquid crystal resin and a thermoplastic resin having a melting point or temperature lower than a liquid crystal transition point of the liquid crystal resin is extruded by an extruder at a temperature not lower than the transition point of the liquid crystal resin. In a second step, a heat-decomposable foaming agent which decomposes at a temperature not lower than the melting point or temperature of the thermoplastic resin but below the liquid crystal transition point of the liquid crystal resin is added to the extruded mixture to melt mix them at a temperature not lower than the melting point or temperature of the thermoplastic resin but below a decomposition initiating temperature of the heat-decomposable foaming agent. In a third step, the mixture thus melt mixed is formed to obtain an expandable, primary mixed resin form. In a fourth step, the expandable, primary mixed resin form is heated to a temperature not lower than the decomposition initiating temperature of the foaming agent but below the liquid crystal transition point of the liquid crystal resin to allow foaming thereof.
In the method for manufacturing a synthetic resin foam, in accordance with the third invention, it is preferred that the thermoplastic resin preferably consists at least partly of a cross-linking resin, and that the method further includes a step of crosslinking the thermoplastic resin after formation of the expandable, primary mixed resin form.
A fourth invention of the present application is a method for manufacturing a synthetic resin foam. The method is characterized as including a first step of supplying to an extruder a liquid crystal resin, a thermoplastic resin having a melting point or temperature lower than a liquid crystal transition point of the liquid crystal resin, and a heat-decomposable foaming agent having a decomposition initiating temperature which exceeds the melting point or temperature of the thermoplastic resin, melt mixing them at a temperature not lower than the melting point or temperature of the thermoplastic resin but below the decomposition initiating temperature of the heat-decomposable foaming agent, and extruding. The method further includes a second step of heating the expandable, primary mixed resin extrusion obtained from the afore-described extruding to a temperature not lower than the decomposition initiating temperature of the heat-decomposable foaming agent and not lower than the liquid crystal transition point of the liquid crystal resin to allow foaming thereof.
In the method for manufacturing a synthetic resin foam, in accordance with the fourth invention, it is preferred that the thermoplastic resin preferably consists at least partly of a cross-linking resin, and that the method further includes a step of crosslinking the thermoplastic resin after the aforesaid first extruding step.
A fifth invention of the present application is a metho
Karukaya Koichi
Kawabata Koshi
Miyazaki Kenji
Arent Fox Kintner & Plotkin & Kahn, PLLC
Foelak Morton
Sekisui Chemical Co. Ltd.
LandOfFree
Expandable synthetic resin composition, synthetic resin... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Expandable synthetic resin composition, synthetic resin..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Expandable synthetic resin composition, synthetic resin... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2562431