Multilayered molding

Details Multilayered molding Multilayered molding

2000-02-16

2004-06-08

Nakarani, D. S. (Department: 1773)

Stock material or miscellaneous articles

Structurally defined web or sheet

Including components having same physical characteristic in...

C428S220000, C428S411100, C428S412000, C428S475800, C428S476100, C428S476300, C428S476900, C428S483000, C428S516000, C428S517000, C428S520000

Reexamination Certificate

active

06746757

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to multilayered moldings. More particularly, it relates to multilayered moldings which comprises thermoplastic resin and have excellent low-temperature impact strength, rigidity, dimensional stability and heat resistance. The multilayered moldings of the present invention are useful for various applications of industrial products, for example, trims (such as bumper) and outside plating (such as fender) of automobiles, housings of electrical and electronic equipment, and building materials such as sound-absorbing walls.
From a view point to attain weight reduction and higher safety of automobiles, many efforts have been made for utilizing the resins in the manufacture of automobile parts such as bumper and fender in place of the conventional metal materials, and the moldings of such resins as polyphenylene ethers, polyamides, polyolefins and polyesters have been partially commercialized by advantages of their excellent qualities such as heat resistance and impact strength.
Nevertheless, it is difficult with the resins to impart the same properties as metals. In the aspect of material, many attempts have been made to blend an impact resistance improver and an inorganic filler in the resin compositions, but these attempts have been unsatisfactory in balance of rigidity and impact strength. In the aspect of molding, researches have been made on the moldings of double-wall structure for realizing improvement of both of rigidity and impact strength, but the obtained moldings are still unsatisfactory in low-temperature impact strength and necessitate designing to a thickness of 8-10 mm in use as a single-layer molding. Thus, such resin moldings cannot be even expected to provide a satisfactory weight-reducing effect as compared with metal materials.
As a result of the present inventors earnest studies to solve the above problem, it has been found that a combination of certain specific kinds of thermoplastic resin composition is effective for providing the useful multilayered moldings having excellent low-temperature impact strength, rigidity, dimensional stability and heat resistance.
The present invention has been attained on the basis of the above finding.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a multilayered molding having an improved balance of properties such as low-temperature impact resistance and rigidity.
To attain the above aim, in an aspect of the present invention, there is provided a multilayered molding comprising at least two of a layer A and a layer B, in which the layers A are formed on both sides of the layer B, each layer A comprises a same or different thermoplastic resin compositions, the layer A has a flexural modulus according to ASTM D790 of not less than 5,000 kg/cm
2
, the layer B comprises a thermoplastic resin composition and has a flexural modulus according to ASTM D790 of not more than 5,000 kg/cm
2
, and the ratio of flexural modulus of the layer A to flexural modulus of the layer B is not less than 5.
DETAILED DESCRIPTION OF THE INVENTION
A detailed description of the present invention is explained as follow.
First, the layer A is explained.
In the present invention, it is essential that the thermoplastic resin composition constituting the layer A has a flexural modulus (as measured according to ASTM D790) of not less than 5,000 kg/cm
2
, preferably not less than 7,000 kg/cm
2
, more preferably not less than 15,000 kg/cm
2
, even more preferably not less than 30,000 kg/cm
2
.
In the present invention, the flexural modulus is defined as a modulus of elasticity in bending measured by a three-point loading system according to ASTM D790.
Examples of the thermoplastic resins constituting the layer A include polyphenylene ethers, polyamides, polycarbonates, saturated polyesters, polyolefins and polyphenylene sulfides. These are explained more specifically below.
The polyphenylene ethers usable for the layer A have a chemical structure represented by the following formula (I):
wherein n is an integer of not less than 50; R
1
, R
2
, R
3
and R
4
represent individually a monovalent substituent selected from the group consisting of hydrogen atom, halogen atom, hydrocarbon groups including no tertiary &agr;-carbon atom, halohydrocarbon groups substituted by halogen atom(s) through at least 2 carbon atoms, hydrocarbonoxy groups, and halohydrocarbonoxy groups substituted by halogen atom(s) through at least 2 carbon atoms.
Examples of the hydrocarbon groups including no tertiary &agr;-carbon atom are lower alkyl groups such as methyl, ethyl, n-propyl, isopropyl, n-butyl and isobutyl; alkenyl groups such as vinyl, allyl, butenyl and cyclobutenyl; aryl groups such as phenyl, tollyl, xylenyl and 2,4,6-trimethylphenyl; and aralkyl groups such as benzyl, phenylethyl and phenylpropyl.
Examples of the halohydrocarbon groups substituted by halogen atom(s) through at least 2 carbon atoms include 2-chloroethyl, 2-bromoethyl, 2-fluoroethyl, 2,2-dichloroethyl, 2- or 3-bromopropyl, 2,2-difluoro-3-iodopropyl, 2-, 3-, 4- or 5-fluoroamyl, 2-chlorovinyl, chloroethylphenyl, ethylchlorophenyl, fluoroxylyl, chloronaphthyl and bromobenzyl.
Examples of the hydrocarbonoxy groups include methoxy, ethoxy, propoxy, butoxy, phenoxy, ethylphenoxy, naphthoxy, methylnaphthoxy, benzyloxy, phenylethoxy and tolylethoxy.
Examples of the halohydrocarbonoxy groups substituted by halogen atom(s) through at least 2 carbon atoms include 2-chloroethoxy, 2-bromoethoxy, 2-fluoroethoxy, 2,2-dibromoethoxy, 2- or 3-bromopropoxy, chloroethylphenoxy, ethylchlorophenoxy, iodoxyloxy, chloronaphthoxy, bromobenzyloxy and chlorotolylethoxy.
The polyphenylene ethers represented by the formula (1) usable for the layer A include the copolymers such as 2,6-dimethylphenol and 2,3,6-trimethylphenol copolymer, 2,6-dimethylphenol and 2,3,5,6-tetramethylphenol copolymer, and 2,6-diethylphenol and 2,3,6-trimethylphenol copolymer. It is also possible to use the so-called modified polyphenylene ethers, e.g. those obtained by graft polymerizing styrene monomers (such as styrene, p-methylstyrene, &agr;-methylstyrene, etc.) to the polyphenylene ethers represented by the formula (1).
These polyphenylene ethers can be produced by the known processes, such as taught in U.S. Pat. Nos. 3,306,874, 3,306,875, 3,257,357 and 3,257,358, Japanese Patent Publication (KOKOKU) No. 52-17880 and Japanese Patent Application Laid-Open (KOKAI) No. 50-51197.
The preferred polyphenylene ethers used in the present invention are those having alkyl substituents at 2 ortho-positions based on the ether/oxygen atom bonds, namely the polyphenylene ethers represented by the formula (1) wherein each of R
2
and R
3
is an alkyl group. Specifically, homopolymer of 2,6-dialkylphenol or 2,3,6-trialkylphenol, and copolymer of 2,6-dialkylphenol and 2,3,6-trialkylphenol are preferred. Also, the polyphenylene ethers used in the present invention preferably have an intrinsic viscosity of 0.25 to 0.70 dl/g (as measured in chloroform at 30° C.). If the intrinsic viscosity is less than 0.25 dl/g, the produced resin composition may be unsatisfactory in impact strength and heat resistance, and if the intrinsic viscosity exceeds 0.7 dl/g, molding workability of the composition may be deteriorated. A high-viscosity polyphenylene ether and a low-viscosity one may be used in combination for improving molding workability of the resin composition.
The polyamide resins usable for the layer A are the ones having —CONH— bonds to the polymer backbone and fusible by heating. The polyamide resins usually have a 3- or more-membered ring lactam, an &ohgr;-amino-acid or a dibasic acid and a diamine as monomer components and can be obtained by ring-opening polymerization or polycondensation. Typical examples of such polyamides are nylon-4, nylon-6, nylon-6.6, nylon-4.6, nylon-12, nylon-6.10, and nylon-11.
Aromatic polyamides including aromatic diamines and aromatic dicarboxylic acids, and the copolymer polyamides including dimerized fatty acids as monomer components are also usable.
The “dim

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