JPS5971352A - Stretched film - Google Patents

Abstract

PURPOSE:To provide a flexible polyvinyl chloride film for stretch packaging, resistant to the lowering of the antifogging property with time, by using a polyglycerol fatty acid ester as the antifogging agent after removing the unreacted glycerol condensate from the ester. CONSTITUTION:100pts.wt. of a polyvinyl chloride resin having an average polymerization degree of about 1,000, e.g. vinyl chloride homopolymer, vinyl chloride/ vinyl acetate copolymer, etc. is compounded with 30-50pts.wt. of a plasticizer (e.g. a combination of dioctyl adipate and an epoxidized vegetable oil) and 0.5- 2.5pts.wt. of an antifogging agent comprising a polyglycerol fatty acid ester from which the unreacted glycerol condensate (2--5-mer). The obtained composition is kneaded under heating, and extruded by T-die process or inflation process to obtain a film having a thickness of 15-30mu. Although the unreacted condensate is preferably removed completely from the ester, a practically satisfiable effect can be attained even if <=2wt% of the condensate is left in the ester.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a flexible polyvinyl chloride film for stretch packaging that is resistant to the adhesion of water droplets and has excellent so-called antifogging properties.

As a method for packaging foods, etc., a soft polyvinyl chloride film is stretched and wrapped around the product, and the ends of the film are made to stick together by simply pressing lightly with a finger or the like on the folded ends of the film to wrap the product. So-called stretch wrapping is used.

The above-mentioned flexible polyvinyl film for stretch packaging (hereinafter referred to as "I'vC stretch film") may have excellent anti-fogging properties that prevent water droplets from adhering to the film surface, depending on how it is used. In response to this demand, various surfactants (antifogging agents) have been added to the above film. As one such antifogging agent, polyglycerin fatty acid ester is excellent in other required qualities such as film transparency, so it can be used alone or in combination with other antifogging agents. is used. However, when the film containing the above-mentioned antifogging agent is used to stretch-wrap contents that are subject to volatilization of water,
Although the anti-fogging property is very excellent in a short period of time after film formation, there is a drawback that the anti-fogging property gradually deteriorates as the time lapse after film formation becomes long.

In order to solve the above-mentioned drawbacks, the present inventors have considered changing the type of other antifogging agent used in combination with polyglycerin fatty acid ester and changing the addition ratio, but no sufficient improvements have been made. I could not do it. Therefore, after further consideration,
It was discovered that a component that inhibits antifogging properties is contained in the polyglycerin fatty acid ester itself. A stretch film characterized in that a polyglycerin fatty acid ester consisting of a fatty acid is added from which an unreacted glycerin condensate has been removed.

The polyvinyl chloride resin used in the present invention includes a homopolymer of vinyl chloride with an average degree of polymerization of about /,000, and a copolymer mainly composed of vinyl chloride, such as a vinyl chloride-vinyl acetate copolymer. included. The above polyvinyl chloride resin contains 30 parts by weight of a plasticizer per 100 parts by weight of the polyvinyl chloride resin in order to impart flexibility and self-adhesiveness to the film.
-! ;Add in a range of 0 parts by weight. As a plasticizer, a combination of dioctyl adipate (DOA) and an epoxidized vegetable oil such as x-poxidized soybean oil is generally used.

Polyglycerin fatty acid ester, which is a commercially available antifogging agent, is a condensate of glycerin (comer to pentamer), that is, G-venter glycerin, reacted with ordinary saturated and unsaturated fatty acids such as lauric acid and stearic acid. This is what I did.

Such commercially available polyglycerin fatty acid esters contain unreacted glycerin condensates, mainly di-glycerin.
/Contains about the weight ratio. Removal of these unreacted substances is a feature of the antifogging agent used in the present invention. Methods for removal include distillation, fractional distillation, and the difference in solubility with water (glycerin condensates are polyglycerin There are methods using fatty acid esters (which have greater water solubility than fatty acid esters). Although it is desirable to completely remove the unreacted glycerin condensate, a practical effect can be obtained if the remaining glycerin condensate has a weight ratio of about 5.2 or less relative to polyglycerin JI]17[ester. The content of the remaining glycerin condensate can be measured by ordinary gas chromatography. It is not clear why the residual glycerin condensate impairs antifogging properties, but considering the phenomenon, glycerin condensates have good solubility in water and poor compatibility with plasticizers, so other preventive agents The glycerin condensate itself on the film surface, which is more easily blown out onto the film surface than the fogging agent composition (so-called blooming phenomenon), has little effect on uniformly wetting water droplets adhering to the film surface, and rather inhibits the effect of polyglycene fatty acid ester. This is thought to be due to the fact that

The amount of the polyglycerin fatty acid ester added is approximately O05 to S, based on 100M parts of the polyvinyl chloride resin.

In the method for producing a film according to the present invention, the above-mentioned composition is heated and mixed using a high-speed mixer or the like, and then extrusion molded using a T-die or an inflation method to obtain a film having a weight of about 30 μS/S to 30 μS.

Next, the effects of the present invention will be clarified through examples.

The basic formulation of the example is polyvinyl chloride resin (P-10!;0)7
00 parts by weight, 35 parts by weight of dioctyl adipate (DOA), 70 parts by weight of epoxidized soybean oil, heat stabilizer (Oa
- Zn-based) 7 parts by weight, and further 5 parts by weight of polyoxyethylene lauryl ether O,S as an antifogging agent and polyglycerin fatty e ester with different contents of unreacted glycerin condensate shown in Table -/. After heating and mixing each of the added formulations using a high-speed mixer, extrusion molding was performed using an inflation method to obtain a film having a thickness of /gμ.

Using this film, a practical antifogging test was conducted and the results are shown in Table 1.

In the practical test, half-split cucumbers were placed in a transparent deep-bottomed tray, the opening of the tray was wrapped with each of the films listed above, and then stored in a refrigerated showcase with an ambient temperature of 3°C.
- After O2, the transparency of the film was observed with the naked eye, and the antifogging property was evaluated on the following scale. Furthermore, after storing the formed film at room temperature for a certain period of time, the above test was conducted and evaluated.

(◎)...The film is good with no clouding at all.

(○): Clouding is observed in some parts of the film, but there is no practical problem.

(△)...The entire surface of the film is cloudy, making it difficult to see the contents.

Table-/ From Table-/, the content of unreacted glycerin condensate is 0 or /
, 5 weight factor shows no deterioration in anti-fogging properties over time and is found to be good as a stretch packaging film. On the other hand, films with an unreacted glycerin condensate content of 5 or 70% by weight have good antifogging properties in the early stage after film formation, but the antifogging properties tend to decrease over time. I understand.

Claims (1)

[Claims] Polyvinyl chloride resin and glycerin condensate (dimer ~ S
1. A stretch film characterized by adding a polyglycerin fatty acid ester consisting of a polyglycerol (glycerol) and a fatty acid, from which unreacted glycerin condensate has been removed.