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US-12617937-B2 - Resin composition and gas-barrier film using same

US12617937B2US 12617937 B2US12617937 B2US 12617937B2US-12617937-B2

Abstract

[Problem] Provided is a resin composition capable of producing a film having an excellent gas-barrier property and a small variation in thickness. [Solution] The resin composition comprises (A) an EVOH-based resin in an amount of at least 40% by weight but 99% by weight or less, (B) a PVA-based resin (B), and (C) an acid-modified polyolefin. The resin composition contains at most 1% of volatile content. The component (B) is preferably a PVA-based resin having a primary hydroxyl group in the side chain.

Inventors

  • Makoto Hatanaka
  • Satoshi IKUBO

Assignees

  • MITSUBISHI CHEMICAL CORPORATION

Dates

Publication Date
20260505
Application Date
20230210
Priority Date
20200918

Claims (20)

  1. 1 . A resin composition comprising (A) EVOH-based resin in an amount of at least 40% by weight but 99% by weight or less; (B) PVA-based resin; and (C) Acid-modified polyolefin; wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1; wherein the ratio [C/(A+B)] of the content of the acid-modified polyolefin (C) to the total sum of the contents of the EVOH-based resin (A) and the polyvinyl alcohol-based (B) resin is 0.02 or more and 0.8 or less, and wherein the resin composition has greater than 0% and at most 1% of a volatile content.
  2. 2 . The resin composition according to claim 1 , wherein the PVA-based resin (B) is contained in an amount of 0.5% by weight or more and 45% by weight or less of the resin composition.
  3. 3 . The resin composition according to claim 1 , wherein the acid-modified polyolefin (C) is contained in an amount of 0.1% by weight or more but less than 45% by weight of the resin composition.
  4. 4 . The resin composition according to claim 1 , wherein the PVA-based resin (B) has a melting point different from a thermal decomposition temperature by 20° C. or more.
  5. 5 . The resin composition according to claim 1 , wherein the PVA-based resin (B) is a PVA-based resin having a primary hydroxyl group in a side chain.
  6. 6 . The resin composition according to claim 1 , wherein the PVA-based (B) resin is a side chain 1,2-diol-containing PVA-based resin having a structural unit represented by the following formula (1), (In the formula (1), R 1 , R 2 , R 3 , R 4 , R 5 and R 6 each independently represents a hydrogen atom or an organic group, and X represents a single bond or a binding chain).
  7. 7 . The resin composition according to claim 1 , wherein the acid-modified polyolefin (C) is a maleic anhydride-modified polyolefin.
  8. 8 . The resin composition according to claim 7 , wherein the maleic anhydride-modified polyolefin is maleic anhydride-modified polyethylene.
  9. 9 . The resin composition according to claim 1 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the PVA-based resin (B) is 40 or less.
  10. 10 . A molded article formed from a resin composition, the resin composition comprising (A) EVOH-based resin in an amount of at least 40% by weight but 99% by weight or less; (B) PVA-based resin; and (C) Acid-modified polyolefin; wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1; wherein the ratio [C/(A+B)] of the content of the acid-modified polyolefin (C) to the total sum of the contents of the EVOH-based resin (A) and the polyvinyl alcohol-based (B) resin is 0.02 or more and 0.8 or less, and wherein the resin composition has greater than 0% and at most 1% of a volatile content.
  11. 11 . A molded article according to claim 10 , wherein the molded article is a film.
  12. 12 . A multilayer structure containing a layer comprising a resin composition, the resin composition which comprises (A) EVOH-based resin in an amount of at least 40% by weight but 99% by weight or less, (B) PVA-based resin, and (C) Acid-modified polyolefin, wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1; wherein the ratio [C/(A+B)] of the content of the acid-modified polyolefin (C) to the total sum of the contents of the EVOH-based resin (A) and the polyvinyl alcohol-based (B) resin is 0.02 or more and 0.8 or less, and wherein the resin composition has at most 1% of a volatile content.
  13. 13 . A building sheet material comprising a resin composition which comprises (A) an EVOH-based resin, (B) a PVA-based resin, and (C) an acid-modified polyolefin, wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1; and wherein the ratio [C/(A+B)] of the content of the acid-modified polyolefin (C) to the total sum of the contents of the EVOH-based resin (A) and the polyvinyl alcohol-based (B) resin is 0.02 or more and 0.8 or less, and wherein the resin composition has greater than 0% and at most 1% of a volatile content.
  14. 14 . The resin composition according to claim 1 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1.1.
  15. 15 . The resin composition according to claim 1 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 2.0.
  16. 16 . The molded article according to claim 10 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1.1.
  17. 17 . The molded article according to claim 10 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 2.0.
  18. 18 . The multilayer structure according to claim 12 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1.1.
  19. 19 . The multilayer structure according to claim 12 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 2.0.
  20. 20 . The building sheet material according to claim 13 , wherein the ratio [A/B] of the content of the EVOH-based resin (A) to the content of the polyvinyl alcohol-based resin (B) is greater than 1.1.

Description

CLAIM FOR PRIORITY This application is a Continuation of PCT/JP2021/032036 filed Sep. 1, 2021, and claims the priority benefit of Japanese application 2020-157179 filed Sep. 18, 2020, the contents of which are expressly incorporated by reference herein in their entireties. TECHNICAL FIELD The present invention relates to a resin composition melt-moldable and capable of providing a film or gas-barrier layer having excellent gas-barrier properties. BACKGROUND A vinyl alcohol-based resin containing a repetitive vinyl alcohol unit, such as polyvinyl alcohol resin and ethylene-vinyl alcohol resin, has an excellent gas-barrier property due to a high crystallinity formed by hydroxyl groups therein. Such vinyl alcohol-based resin is used as a packaging film or gas-barrier layer in a package or container for leisure tools, toys, miscellaneous goods, daily necessities, parts, and the like, in a wide variety of fields including agricultural, civil engineering, industrial, and medical field, based on the excellent gas-barrier property. From the viewpoint of its productivity of a laminate or a molded article, a vinyl alcohol-based resin used as a gas-barrier layer for a packaging film is required to be melt moldable. Among vinyl alcohol-based resins containing a repetitive vinyl alcohol unit, polyvinyl alcohol (PVA) has a high content of vinyl alcohol units and exhibits excellent gas-barrier property. However, the PVA has a decomposition temperature close to its melting point, which causes to be difficult in hot-melt molding. For this reason, using the PVA alone for a packaging material or the gas-barrier layer of the melt-molded article is actually limited. In this regard, ethylene-vinyl alcohol-based resin (EVOH-based resin), which is a copolymer of ethylene and vinyl alcohol, can be melt-molded. EVOH-based resin may be used alone as a gas-barrier layer for a packaging material or a melt-molded article. However, an enhanced gas barrier property is demanded for the EVOH-based resin. JP H07-179709 A (Patent Document 1) proposes a melt moldable resin composition having an excellent gas-barrier property. The resin composition comprises a polyvinyl alcohol in an amount of 40 to 80% by weight, an EVOH in an amount of 5 to 40% by weight, a thermoplastic resin having a softening temperature of 130° C. or less in an amount of 1 to 15% by weight, and polyethylene glycol in an amount of 5 to 15% by weight. The resin composition disclosed in the patent document 1, employs a PVA having a polymerization degree of 300 to 3500, preferably 500 to 2000 and a saponification degree of 95 mol % or less from the viewpoint of film strength and moldability. In the patent document 1, the resin composition was evaluated with respect to oxygen permeability of the multilayer film containing a core layer of the resin composition. The multilayer film was produced by blown film extrusion using a 4-type and 5-layer comparison and was also evaluated with respect to the state of multilayer film immediately after the blown film extrusion. PRIOR ART Patent Document [Patent Document 1] JP H07-179709A SUMMARY OF THE INVENTION Technical Problem to be Solved by the Invention In the Patent Document 1, a 4-type and 5-layer comparison was prepared and subsequently oriented to produce a 4-type and 5-layer film. In the case of a resin composition prepared by adding a melt-moldable thermoplastic resin having a low softening temperature or a low melting point to a mixture of a PVA and an EVOH, the resin composition forms a film having a great variation in thickness. Such a film is inferior in moldability, which is a problem. The present invention has been made under the circumstances. The purpose of the invention is to provide a resin composition exhibiting excellent moldability that can produce a film with excellent gas-barrier property and suppressed variation in thickness. Means for Solving the Problem A resin composition of the present invention comprises (A) an EVOH-based resin in an amount of more than 40% by weight but 99% by weight or less, (B) a PVA-based resin, and (C) an acid-modified polyolefin, wherein the resin composition has a volatile content of 1% or less. A preferable content of the PVA-based resin (B) is 0.5% by weight or more but less than 59.9% by weight. A preferable content of the acid-modified polyolefin (C) is 0.1% by weight or more but less than 45% by weight. A preferable PVA-based resin (B) has a melting point differing from its thermal decomposition temperature by 20° C. or more. In another aspect, a preferable PVA-based resin (B) has a primary hydroxyl group in the side chain. A side chain 1,2-diol-containing PVA-based resin having a structural unit represented by the following formula (1) is particularly preferred. In the formula (1), R1, R2, R3, R4, R5 and R6 each independently represents a hydrogen atom or an organic group, and X represents a single bond or a binding chain. A preferable acid-modified polyolefin (C) is a maleic anh