Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-06-11
2001-10-16
Short, Patricia A. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S064000, C525S09200D, C525S125000, C525S131000, C525S166000, C525S173000, C525S179000
Reexamination Certificate
active
06303689
ABSTRACT:
INDUSTRIAL FIELD OF APPLICATION
The present invention relates to a method of producing a thermoplastic resin composition, and to moulded articles thereof. Its objective lies in offering a method of manufacturing a resin composition having outstanding extrusion moulding properties, and the water vapour permeability of which can be controlled over a broad range while maintaining uniform performance, transparency, antistaticity and high gas permeability; together with moulded articles or packaging materials formed therefrom.
PRIOR-ART
Hitherto, on account of their ease of handling and balanced properties, thermoplastic resins such as polyolefins have been widely used in applications of various kinds, and they are also useful as packaging materials. In such circumstances, various materials have been devised and employed according to the particular objectives, ranging from permeable films of high gas permeability to barrier materials of low permeability, depending on the particular material, but few are endowed with high water vapour permeability. For example, techniques are known for blending or laminating a material of high permeability and a material of low permeability. However, when used for the storage of foodstuffs, problems have arisen such as the condensing of the water vapour in the interior to form adhering water droplets so that the contents are difficult to see, or the condensed moisture hastens the deterioration of the contents and rotting readily occurs. Again, in cases where longer term storage has been tried, there have been limits to the control of the gas permeability.
In order to resolve such difficulties, there is known the introduction of fine pores into the film either mechanically by means of a needle or the like or physico-chemically with a laser or the like, with the permeability being controlled by the hole diameter and the density of the holes present (see, for example, Japanese Unexamined Patent Publication Nos 47-23478, 62-148247 and 2-85181, etc). Again, there has been proposed the raising of the water vapour permeability by locally greatly thinning the film without introducing holes. However, with these methods there is a great difference in the permeability between the pore regions and the other regions, and not only is it difficult to obtain uniformity over the entire film but there is also the disadvantage that the film strength is lowered and the selectivity of the gas permeability is reduced.
Now, methods have also been proposed which abandon the concept of raising the permeability of the film itself and where, instead, a gas is sealed inside which controls the metabolic action, or where there is introduced an adsorbent for the harmful gases and moisture (see, for example, Japanese Unexamined Patent Publication No. 3-14480, etc). However, as well as being time-consuming, the effects of these methods are not altogether adequate.
On the other hand, compositions comprising a polyether-containing block polyamide or the like, along with a polyolefin and/or a functional polyolefin are known (see, for example, Japanese Unexamined Patent Publication No. 1-163234, and European Patent Nos 459862, 475963, 559284, 657502 and 675167, etc). As the effects thereof, moisture permeability, high impact properties and anti-static properties, etc, are described. However, these compositions comprising polyether-containing block polyamides and polyolefins have poor mouldability even when a compatibilizing agent is incorporated, and articles of stable product quality are hard to obtain.
PROBLEM TO BE RESOLVED BY THE INVENTION
As a result of intensive investigation aimed at controlling the water vapour permeability within a desired range with good reproducibility, while retaining high gas permeability and, moreover obtaining uniform performance, such as transparency or antistaticity, the present inventors discovered that these objectives could be attained by employing the so-called master batch method in which a high concentration of reactive compound is first blended, and then dilution and reaction effected in stepwise fashion. It is on this discovery that the present invention is based.
MEANS FOR RESOLVING THE PROBLEM
The present invention is a method of manufacturing a thermoplastic resin composition which is characterized in that, when blending a polymer (A) containing polyether chains as structural units and a polyolefin (B), the polymer (A) containing polyether chains as structural units is first melt-blended with a copolymer (C) of a vinyl compound and an unsaturated dicarboxylic acid or derivative thereof and/or a compatibilizing agent (D), after which the polyolefin (B) is then blended; together with moulded articles and packaging materials obtained by this method.
It is clear that the polymer (A) is first melt blended with (C) only or with (D) only or with (C) and (D).
In the present invention, ‘polymer (A) containing polyether chains as structural units’ refers to block copolymer in which polyoxyalkylene chains and other polymer chains are linked together or to a polymer in which polyoxyalkylene chains are combined together via coupling regions. Here as examples of the polyoxy-alkylene, there can be cited polyoxyethylene, poly(1,2- and 1,3-oxypropylene), polyoxytetramethylene, polyoxy-hexamethylene, ethylene oxide and propylene oxide block or random copolymers, and ethylene oxide and tetra-hydrofuran block or random copolymers. In particular, a polyoxyalkylene having from 2 to 4 carbons in the alkylene moiety is preferred, with polyoxyethylene being most preferred. The number average molecular weight of the polyoxyalkylene is from 200 to 6000, and preferably from 300 to 4000.
In the present invention, as examples of the ‘polymer (A) containing polyether chains as structural units’ desirably used, there are polyetherpolyamide block copolymers, polyetherpolyester block copolymers and polyetherurethanes. Of these, the polyetherpolyamide block copolymers are especially preferred.
The ‘polyetherpolyamide block copolymer’ used in the present invention is a block copolymer in which there are linked together polyoxyalkylene chains (a) and polyamide chains (b) which comprise polymer of an aminocarboxylic acid or lactam having at least six carbons, or polymer of the salt of dicarboxylic acid and diamine with at least six carbons. Where (a) and (b) are alternately linked together via a dicarboxylic acid having from 4 to 20 carbons, the copolymers are generally referred to as polyetheresteramides, and these are also included in the invention. Here, as the ‘aminocarboxylic acid or lactam having at least six carbons, or polymer of the salt of a dicarboxylic acid and diamine with at least six carbons’, there are preferably used 11-aminoundecanoic acid, 12-aminododecanoic acid, caprolactam, laurolactam, hexamethylenediamine/adipic acid salt, hexamethylenediamine/sebacic acid salt or the like. Further, in regard to aforesaid components (a) and (b), two or more types may also be jointly used together.
Such polymer is produced, for example, by the method described in Japanese Examined Patent Publication No. 56-45419. The types and amounts of the polyether and polyamide components in the block copolymer used in the present invention are selected according to the objectives and application. From the point of view of water vapour permeability, water resistance and the handling characteristics, etc, the polyether/polyamide ratio is preferably from 4/1 to 1/4.
The ‘polyetherpolyester block copolymer’ employed in the present invention is one in which there are linked together polyoxyalkylene chains (a) and polyester chains (d) comprising polymer of a hydroxycarboxylic acid with at least six carbons or of a dihydroxy compound with at least two carbons and an aromatic dicarboxylic acid. Again, in regard to these (a) and (d) components, two or more types may be jointly employed. Such polymer is produced for example by the method described in U.S. Pat. No. 4,739,012. The weight ratio of the aforesaid (a) and (d) components in the block copolymer employed in the present invention is det
Ishino Kiyotaka
Kuratsuji Takatoshi
Maillet Jerome
Atofina
Millen White Zelano & Branigan P.C.
Short Patricia A.
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