Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2001-07-17
2003-04-15
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S047000, C523S124000
Reexamination Certificate
active
06548577
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wood-filled thermoplastic resin composition and a process for producing the same.
2. Description of the Related Art
Heretofore, a thermoplastic resin composition containing wood meal is well known as a raw material for interior members in automobiles, etc.
However, thermoplastic resins such as polyethylene and polypropylene are generally non-polar while the wood meal has polar groups such as hydroxyl group, so that the affinity between the wood meal and thermoplastic resin particles is low, and by mere mixing thereof, the wood meal and thermoplastic resin particles are not combined, thus failing to form a stable composition. Accordingly, it was necessary for preparation of the above composition that wood meal is introduced into a molten thermoplastic resin liquefied by heating, and the wood meal is impregnated with, and absorbed by, the thermoplastic resin to unify them (Japanese examined patent application JP 59-49188-B).
In such a method, however, the wood meal scatters significantly upon mixing of the wood meal with the thermoplastic resin particles, and further the thermoplastic resin is melted and kneaded with the wood meal at high temperatures to cause a nasty smell significantly by “burning” of the wood meal, thus leading to many problems in the operativeness and working atmosphere.
To improve the affinity between the wood meal and thermoplastic resin particles, a method wherein an ethylene/organic acid (e.g. maleic acid) copolymer or modified polypropylene is added prior to melting and kneading of the thermoplastic resin particles with the wood meal is also proposed (Japanese examined patent applications JP 59-30176-B & JP-B 64-1503-B). Although the affinity is improved in such a method, it is not always possible to solve problems such as scattering of wood meal and a nasty smell upon melting and kneading, and further the concentration of chargeable wood meal is up to about 50% by weight, and if the wood meal is added in an amount exceeding this concentration, there easily occurs the separation of the wood meal from the thermoplastic resin particles as well as the bridge formation thereof in a molding hopper, and the wood meal is dispersed heterogeneously, thus causing problems such as a defect in the outward appearance of moldings.
SUMMARY OF THE INVENTION
Under these circumstances, the present inventors made much study for developing a wood-filled thermoplastic resin composition free of problems such as scattering of wood meal and a nasty smell due to burning, in which wood meal can be dispersed uniformly at a high concentration of charged wood meal, and as a result, the present invention was reached.
That is, the present invention provides a wood-filled thermoplastic resin composition, comprising wood meal, thermoplastic resin particles and a binder solution.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising”, will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integer or step.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention is described in detail.
In the wood-filled thermoplastic resin composition of the present invention, finely divided materials or sawdust from known wood can be used as the wood meal, but use of waste wood is more economically advantageous.
The material of wood meal is not particularly limited, but conifers such as a Japanese cypress, a Japanese hemlock etc. are preferable to confer mechanical strength on moldings formed from the wood-filled thermoplastic resin composition.
If the particle diameter of the wood meal is too large, the affinity between the wood meal and the thermoplastic resin particles is lowered, and thus the maximum particle diameter of at least 80% of the particle group constituting the wood meal is preferably 2 mm or less.
The thermoplastic resin in the thermoplastic resin particles includes polyolefins such as polypropylene and polyethylene, acrylonitrile-styrene-butadiene block copolymers, polystyrene, polyamide such as nylon, polyester, polyvinyl chloride, polycarbonate, acryl resin, and thermoplastic elastomers such as EPM (ethylenepropylenediene copolymers), and they are used singly or as a mixture thereof, or as a polymer alloy using them. Among them, polyethylene and polypropylene are used preferably and particularly polypropylene excellent in heat resistance is preferably used.
Such thermoplastic resin particles may have an arbitrary shape e.g. sphere, pellet or cube, and is not particularly limited, but the maximum particle diameter of at least 80% of the particle group constituting the thermoplastic resin particles is preferably 2 mm or less.
The binder in the binder solution has a function as a sticking agent for sticking the wood meal on the thermoplastic resin particles, and is not particularly limited insofar as it has such a function, and in particular water-soluble high hydrogen bonding resins such as polyvinyl alcohol, polyvinyl ether, polyvinyl pyrrolidone, sodium polyacrylate and polyacrylamide are desirably used. Among them, polyvinyl alcohol excellent in heat resistance is preferably used.
Such a binder is used as a solution, and as the solvent therefor, any solvents capable of dissolving said binder can be used without particular limitation, and examples thereof include water and various kinds of conventionally used organic solvents such as aliphatic hydrocarbons such as hexane and heptane, aromatic hydrocarbons such as toluene and xylene, alcohols such as methyl alcohol, ethers such as ethyl ether and dioxane, ketones such as acetone, and esters such as ethyl acetate.
Such solvent may be selected suitably depending on the binder to be used, and a single solvent or a mixture of two or more solvents may be used.
If a mixture of two or more solvents is used, the solvents are used preferably as a uniform mixture in which they are miscible with one another, but insofar as the binder is dissolved in some or all the solvents to form a solution, the solvents may also be used as a heterogeneous mixture.
It is preferable for safety and handling that among such solvents, water alone or a mixed solvent of water and a hydrophilic solvent is used and thus the binder solution is used as an aqueous solution or as a solution in a mixed solvent of water and a hydrophilic solvent, and particularly when the binder is a water-soluble high hydrogen bonding resin, the binder solution is used preferably as an aqueous solution.
In the wood-filled thermoplastic resin composition of the present invention, the compounding ratio of the wood meal and thermoplastic resin particles is determined depending on the intended use of the final product, and is not particularly limited, but usually the compounding ratio by weight of wood meal/thermoplastic resin particles is in the range of from 10/90 to 80/20, and since compounding of wood meal in a larger amount is economically advantageous, the compounding ratio is preferably in the range of from 50/50 to 80/20, more preferably from 50/50 to 70/30.
The amount of the binder solution is not particularly limited either, and is suitably determined depending on various conditions such as the kinds and shape of the wood meal, the size of the particles of the wood meal, the compounding ratio of the wood meal/the thermoplastic resin particles, the shape of the thermoplastic resin particles, and
Katagiri Shiro
Kitayama Takeo
Matsubara Shigeyoshi
Fitch Even Tabin & Flannery
Ribar Travis B
Seidleck James J.
Sumitomo Chemical Company Limited
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