JP-7855345-B2 - polyvinylidene chloride resin wrap film

Inventors

• 竹林 新二
• 吉田 謙次
• 小山 純一郎

Assignees

• 旭化成株式会社

Dates

Publication Date

20260508

Application Date

20211222

Claims (4)

1. A vinylidene chloride-based resin wrap film, A vinylidene chloride-based resin wrap film is obtained by dissolving the vinylidene chloride-based resin wrap film in tetrahydrofuran and reprecipitation with methanol to obtain a polymer, which is then thermally extracted with a chloroform and methanol mixed solution at 50°C (chloroform/methanol volume ratio = 65/35), comprising (A) a vinylidene chloride copolymer oligomer and (B) at least one additive selected from the group consisting of epoxidized fatty acid ester compounds, citrate esters, dibasic acid esters, and acetylated fatty acid glycerides, wherein the weight-average molecular weight of the thermal extract containing (A) and (B) is 3,000 to 7,000, the content of the thermal extract is 0.5 to 3.0% by mass relative to the wrap film, and the thickness is 6 to 18 μm.
2. The vinylidene chloride-based resin wrap film according to claim 1, wherein the peak top molecular weight of the vinylidene chloride copolymer oligomer contained in the heat extract is 4,000 to 8,000.
3. The vinylidene chloride-based resin wrap film according to claim 1 or 2, wherein the amount of residual additives contained in the heat extract is quantified by NMR, and the amount obtained by subtracting the total amount of residual additives from the amount of the heat extract is 0.3 to 1.8% by mass relative to the wrap film.
4. A vinylidene chloride-based resin wrap film according to any one of claims 1 to 3, wherein the 2% tensile modulus in the MD direction is 250 to 600 MPa.

Description

This invention relates to a vinylidene chloride-based resin wrap film. Traditionally, polyvinylidene chloride (PVC) plastic wrap films have been widely used in households as simple packaging materials for food and other items due to their excellent adhesion and gas barrier properties. In recent years, however, consumers have strongly demanded higher functionality from PVC plastic wrap films. In particular, there is a need for good release properties while ensuring adequate adhesion. Adhesion refers to how easily the wrap film adheres to the container when used. Pull-out ease refers to how easily the wrap film, when stored on a core, can be pulled out of the storage box. Generally, if the film adheres too tightly to itself, it becomes difficult to pull out; therefore, there is a trade-off between adhesion and pull-out ease. Patent Document 1 describes a technology for polyvinylidene chloride-based resin wrap films having a specific molecular structure. Furthermore, attempts have been made to control various properties by defining the amount of low-molecular-weight components contained in polyvinylidene chloride resin wrap film. Patent documents 2 and 3 describe techniques for defining extracts obtained by extracting polyvinylidene chloride resin wrap film with methanol. Japanese Patent Publication No. 2018-24720International release WO2014/054413International release WO2014/054414 This is a schematic diagram of an example of the apparatus used in the film-forming process of the present invention.This is one example of how the film of the present invention can be used. The following describes in detail embodiments for carrying out the present invention (hereinafter referred to as "this embodiment"). However, the present invention is not limited to the following embodiments and can be implemented in various modifications within the scope of its gist. The polyvinylidene chloride-based resin wrap film according to this embodiment is The polymer obtained by dissolving the wrap film in tetrahydrofuran and reprecipitation with methanol is thermally extracted with a chloroform and methanol mixed solution at 50°C (chloroform/methanol volume ratio = 65/35). The weight-average molecular weight of the thermal extract is 3,000 to 7,000, the content of the thermal extract is 0.5 to 3.0% by mass relative to the wrap film, and the thickness is 6 to 18 μm. The polyvinylidene chloride-based resin wrap film according to this embodiment comprises (1) a vinylidene chloride-based copolymer as the main component, (2) a heat extract obtained by heat extraction under specific conditions, and (3) additives that are added as needed. When the polyvinylidene chloride-based resin wrap film according to this embodiment is dissolved in tetrahydrofuran and reprecipitated with methanol, additives such as plasticizers, adhesives, tackifiers, and stabilizers (components of (3) above) mainly elute into the methanol. When the polymer reprecipitated with methanol is further thermally extracted with a chloroform and methanol mixed solution at 50°C (chloroform/methanol volume ratio = 65/35), the thermal extract (components of (2) above) elutes into the chloroform and methanol mixed solution (chloroform/methanol volume ratio = 65/35). The residue remaining after extraction with the chloroform and methanol mixed solution (chloroform/methanol volume ratio = 65/35) mainly consists of the vinylidene chloride-based copolymer (components of (1) above). As a result of diligent research by the inventors, it was found that the thermal extract obtained by further heat-extracting the polymer after methanol reprecipitation with a chloroform and methanol mixed solution (chloroform/methanol volume ratio = 65/35) at 50°C contained compounds with a specific molecular weight range. These compounds bleed onto the film surface and spread throughout the film, resulting in improved adhesion and drawability. The polymer after methanol reprecipitation was further thermally extracted using a chloroform and methanol mixed solution at 50°C (chloroform/methanol volume ratio = 65/35). The resulting thermal extract contained compounds with molecular weights within a specific range, and it was found that these compounds could not be extracted using solvents such as acetone or methanol, as described in Patent Documents 2 or 3. (Polyvinylidene chloride resin) The vinylidene chloride resin is not particularly limited as long as it contains vinylidene chloride repeating units. For example, vinylidene chloride copolymer A contains vinylidene chloride repeating units and monomer repeating units copolymerizable therewith. Monomers copolymerizable with vinylidene chloride are not particularly limited, but examples include vinyl chloride; acrylic acid esters such as methyl acrylate and butyl acrylate; methacrylic acid esters such as methyl methacrylate and butyl methacrylate; acrylic acid, methacrylic acid; acrylonitrile; vinyl acetate, etc. These monomers may be used individually or in