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
1999-02-09
2003-06-10
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S066000, C525S069000, C525S123000, C525S177000, C525S184000, C428S035100
Reexamination Certificate
active
06576705
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a thermoplastic resin composition and moulded articles thereof. The objective lies in providing a resin composition which, while maintaining high gas permeability, permits water vapour permeability to be controlled over a broad range; together with moulded articles or packaging materials comprising this composition, in particular a packaging material for foodstuffs like fruit and vegetables.
BACKGROUND OF THE INVENTION
Thermoplastic resins such as polyolefins have been widely used hitherto in applications of various kinds on account of their ease of handling and good balance of properties, and they are also valuable as packaging materials. In such circumstances, depending on the resin used, various types of material can be designed and employed according to the particular objectives, ranging from permeable films with high gas permeability to barrier materials with low permeability, but few are endowed with high water vapour transmission. Techniques are known where, for example, a highly permeable material and a material of low permeability are blended or laminated. However, when used for storing foodstuffs, there have been problems such as water vapour condensing in the interior and water droplets adhering, so that the interior cannot be viewed, or the condensed moisture hastens deterioration of the contents and rotting tends to occur. Moreover, there have been limits to the control of gas permeability where longer term storage has been attempted.
For the purposes of resolving these difficulties, there is known the introduction of minute holes in the film either mechanically by means of a needle, etc, or physicochemically by means of a laser, etc, with the permeability being controlled by hole diameter and the density of such holes present (see, for example, Japanese Unexamined Patent Publication Nos 47-23478, 62-148247 and 2-85181, etc). Further, there has been proposed raising the water vapour permeability by producing extremely thin regions locally in the film without going so far as to introduce holes. However, in these methods, not only is there a considerable difference in permeability between the fine hole regions and other regions so that it is difficult to obtain uniformity over the film as a whole, but there are also problems such as the film strength being weakened and the selectivity of the permeability being reduced.
On the other hand, methods have also been proposed in which any attempts at raising the permeability of the film itself are abandoned, so that the gases which control metabolic action are trapped inside, and instead an adsorbent for the harmful gases and moisture is introduced (see, for example, Japanese Unexamined Patent Publication No. 3-14480, etc). However, such methods are troublesome and, moreover, their effect is not necessarily adequate.
Now, compositions comprising a polyether-containing block polyamide, etc, along with a polyolefin and/or functional polyolefin are already known (see, for example, Japanese Unexamined Patent Publication No. 1-163234, and European Patent Publication Nos 459862, 475963, 559284, 657502 and 675167, etc). As effects, there are described moisture transmission, high impact resilience and antistatic properties, etc. However, only a general description is given of the polyolefin, and there is no mention of paying attention to the density thereof to control the gas permeability.
DESCRIPTION OF THE INVENTION
The present invention has been made based on the discovery that, in trying to control the water vapour permeability within a desired range while maintaining a high gas permeability, this objective may be realised by incorporating resin of specified density.
The present invention is a thermoplastic resin composition which is characterized in that a polymer (A) containing polyether chains as structural units, polyethylene or copolymer in which polyethylene is the chief component (B) of density as specified in JIS K6760 of less than 0.91 g/cm
3
and a compatibilizing agent (C) are blended in proportions by weight of A/B/C=99.5 to 0.5/0.5 to 99.5/0 to 30 (where A+B+C=100); together with moulded articles or packaging materials thereof.
In the present invention, the ‘polymer (A) containing polyether chains as structural units’ means a block copolymer in which polyoxyalkylene chains and other polymer chains are linked together, or a polymer in which polyoxyalkylene chains are connected together via coupling regions. Examples of the polyoxyalkylene here are polyoxyethylene, poly(1,2- and 1,3-oxypropylene), polyoxytetramethylene, polyoxyhexamethylene, ethylene oxide and propylene oxide block or random copolymers, ethylene oxide and tetramethylene oxide block or random copolymers, and the like. In particular, those with from 2 to 4 carbons in the alkylene moiety are 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.
The preferred ‘polymer (A) containing polyether chains as structural units’ employed in the present invention is a polyether-polyamide block copolymer, polyether-polyester block copolymer or polyether-urethane. Amongst these, the polyether-polyamide block copolymer is especially preferred.
The ‘polyether-polyamide block copolymer’ used in the present invention is a polymer in which there are linked together polyoxyalkylene chains (a) and polyamide chains (b), where the latter comprises polymer of an aminocarboxylic acid or lactam with six or more carbons, or of a salt of dicarboxylic acid and diamine with at least six carbons. Where (a) and (b) are connected together via a dicarboxylic acid with from 4 to 20 carbons, the material is generally referred to as a polyetheresteramide, and this too will be included in the invention. Here, as the ‘aminocarboxylic acid or lactam with six or more carbons, or salt of dicarboxylic acid and diamine with at least six carbons’, there is preferably used 11-aminoundecanoic acid, 12-aminododecanoic acid, caprolactam, laurolactam, hexamethylenediamine/adipic acid salt or hexamethylene-diamine/sebacic acid salt, etc. Further, two or more types of the aforesaid (a) and (b) components can be used together.
This polymer is produced, for example, by the method described in Japanese Examined Patent Publication No. 56-45419, etc. Specific examples of such polymers are Pebax (Elf Atochem), ELY (EMS) and Vestamid (Hòls), etc. The type and weight ratio 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 properties, etc, a polyether/polyamide ratio of from 4/1 to 1/4 is preferred.
The ‘polyether-polyester block copolymer employed’ in the present invention is a polymer in which there are linked together polyoxyalkylene chains (a) and polyester chains (d), where the polyester is a polymer of a hydroxycarboxylic acid with six or more carbons, or of a dihydroxy compound with two or more carbons and an aromatic dicarboxylic acid. Further, two or more types of these (a) and (d) components can be jointly used. This polymer is, for example, produced by the method described in U.S. Pat. No. 4,739,012. Specifically, there can be cited Hytrel (DuPont), Pelprene P type (Toyobo) and Rekuse (Teijin). The weight ratio of the aforesaid (a) and (d) components in the block copolymer used in the present invention will be determined by the objectives and application. Although being thermoplastic polyester elastomers in the same way, with polyester-polyester block copolymers (for example Pelprene S type) here is little effect.
The ‘polyether-urethane’ employed in the present invention is a thermoplastic polyurethane in which the polyether is used as the soft segments. There is little effect with polyester type or caprolactone type polyurethanes. Specifically, the polyether-urethane is normally obtained by the reaction of an organic di-i
Bouilloux Alain
Germain Yves
Kuratsuji Takatoshi
Maillet Jerome
Elf Atochem S.A.
Gorr Rachel
Smith , Gambrell & Russell, LLP
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