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
2002-05-08
2004-07-20
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...
C524S439000
Reexamination Certificate
active
06765070
ABSTRACT:
The present invention relates to a copolymerized polyester resin composition and a stretched film. Particularly, it relates to a copolymerized polyester resin composition whereby a heat shrinkable film excellent in heat shrinkability, mechanical strength, transparency, solvent adhesive properties, etc. can be obtained, and a stretched film made thereof.
Heretofore, heat shrinkable films have been widely used, for example, as packaging materials, binding materials, covering materials, sealing materials or labeling materials, by utilizing such a nature that when heated, they shrink to provide a binding force. Particularly, an attention has been drawn to heat shrinkable films made of monoaxially or biaxially stretched films of polyethylene terephthalate resins in view of the excellent mechanical strength, chemical properties, transparency, gas barrier properties, safety and sanitation and the like, of polyester resins. They have shown a rapid increase in demand along with a recent increase in demand of bottles for beverages, made of polyethylene terephthalate resins, as labeling materials to cover the outer surfaces of such bottles, as they are advantageous from the viewpoint of recycling of bottles, since the labeling materials are of the same material as the bottles.
However, polyethylene terephthalate resins are crystalline, and at the same time, their glass transition temperatures and heat shrinkage-initiating temperatures are high. Further, the shrinkage is inadequate. There is a further problem that no adequate bond strength can be obtained by solvent bonding, and the bond strength tends to decrease as time passes.
On the other hand, in order to solve the above problems, a copolymerized polyester obtained by copolymerizing terephthalic acid and/or isophthalic acid, naphthalene dicarboxylic acid, ethylene glycol and other diol components (see e.g. JP-A-8-239460), a copolymerized polyester made of terephthalic acid, ethylene glycol, cyclohexane dimethanol and butanediol (see e.g. JP-A-8-27260) or a heat shrinkable polyester film made of a resin composition comprising a polyethylene terephthalate polyester having neopentyl glycol copolymerized, a polybutylene terephthalate and a polyethylene terephthalate (see e.g. JP-A-7-216109) has, for example, been proposed.
JP-A-59-97175 discloses a polyester shrinkable label excellent in low temperature heat shrinkability, which is made of an aromatic dicarboxylic acid component and a diol component, wherein the diol component comprises from 50 to 99 wt % of a copolyester wherein 1,4-cyclohexanedimethanol is present in an amount of from 10 to 40 mol %, and from 1 to 50 wt % of polybutylene terephthalate.
However, by a study conducted by the present inventors, it has been found that it is impossible to obtain a heat shrinkable polyester film which fully satisfies the requirements for heat shrinkage, bond strength by a solvent, transparency, film strength, etc. even by means of the above copolymerized polyesters or resin compositions. The present invention has been made under these circumstances, and it is an object of the present invention to provide a copolymerized polyester resin composition whereby a heat shrinkable film excellent in the heat shrinkability, mechanical strength, transparency, solvent bonding properties, etc., can be obtained, and a stretched film made of such a resin composition.
The present inventors have conducted an extensive research and as a result, have found that a polyester resin composition comprising a certain specific copolymerized polyethylene terephthalate resin obtained by using isophthalic acid and cyclohexane dimethanol as copolymerized components, and a polybutylene terephthalate resin in certain specific proportions, is capable of attaining the above object. The present invention has been accomplished on the basis of this discovery.
Namely, in a first aspect, the present invention provides a copolymerized polyester resin composition comprising the following polyethylene terephthalate resin (A) and a polybutylene terephthalate resin (B), wherein the proportion of the resin (A) is from 50 to 95 wt %, and the proportion of the resin (B) is from 5 to 50 wt %, based on the total amount of the resins (A) and (B):
Resin (A): a copolymerized polyethylene terephthalate resin, having a dicarboxylic acid component containing terephthalic acid as the main component and a diol component containing ethylene glycol as the main component copolymerized, wherein the dicarboxylic acid component contains isophthalic acid in an amount of from 3 to 30 mol % based on the total dicarboxylic acid component, and the diol component contains a cyclohexane dimethanol in an amount of from 3 to 40 mol % based on the total diol component.
In a second aspect, the present invention provides a stretched film made of such a resin composition.
In a third aspect, the present invention provides a heat shrinkable film made of such a resin composition.
Now, the present invention will be described in further detail with reference to the preferred embodiments.
The copolymerized polyester resin composition of the present invention (hereinafter referred to simply as the resin composition) comprises the specific copolymerized polyethylene terephthalate resin (A) and the polybutylene terephthalate resin (B).
In the present invention, the copolymerized polyethylene terephthalate resin (A) (hereinafter sometimes referred to as the resin (A)) is a copolymerized polyethylene terephthalate resin, having a dicarboxylic acid component containing terephthalic acid as the main component and a diol component containing ethylene glycol as the main component copolymerized, wherein the dicarboxylic acid component contains isophthalic acid in an amount of from 3 to 30 mol % based on the total dicarboxylic acid component, and the diol component contains a cyclohexane dimethanol in an amount of from 3 to 40 mol % based on the total diol component.
In the forgoing, “containing terephthalic acid as the main component” means that at least 50 mol % of the total dicarboxylic acid component is terephthalic acid, and the proportion of terephthalic acid in the total dicarboxylic acid component is preferably at least 70 mol %, more preferably at least 75 mol %. Likewise, “containing ethylene glycol as the main component” means that at least 50 mol % of the total diol component is ethylene glycol, and the proportion of ethylene glycol in the total diol component is preferably at least 65 mol %, more preferably at least 70 mol %.
If the copolymerized amount of isophthalic acid is less than 3 mol %, the heat shrinkability of the resulting film tends to be poor, and if the copolymerized amount of isophthalic acid exceeds 30 mol %, the mechanical strength of the resulting film tends to be poor. The copolymerized amount of isophthalic acid is preferably at least 4 mol %, more preferably at least 5 mol %. On the other hand, it is preferably at most 25 mol %, more preferably at most 20 mol %.
If the copolymerized amount of cyclohexane dimethanol is less than 3 mol %, the bond strength by a solvent, of the resulting film, tends to be poor, and if the copolymerized amount of cyclohexane dimethanol exceeds 40 mol %, the heat stability of the resulting resin composition tends to be low, and consequently, the mechanical strength of the resulting film tends to be poor. The copolymerized amount of cyclohexane dimethanol is preferably at least 5 mol %, more preferably at least 10 mol %. On the other hand, it is preferably at most 35 mol %, more preferably at most 30 mol %.
The cyclohexane dimethanol may, for example, be 1,1-cyclohexane dimethanol, 1,2-cyclohexane dimethanol, 1,3-cyclohexane dimethanol, or 1,4-cyclohexane dimethanol. Among them, 1,4-cyclohexane dimethanol is preferred.
In the present invention, the resin (A) may be one having a dicarboxylic acid component other than terephthalic acid and a diol component other than ethylene glycol further copolymerized, so long as the dicarboxylic acid component contains terephthalic acid as the main component, and the diol component cont
Kanbe Toshio
Keitoku Fumio
Tamura Koichi
Tomita Yasuhiro
Mitsubishi Chemical Corporation
Short Patricia A.
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