Kureha Kagaku Kogyo Kabushiki Kaisha

Kureha Corporation

Takahisa Ueyama

Tadayoshi Itoh

Yoshihiro Matsukura

Hajime Tsukamoto

Yuta Sekiya

Eiichi Hayashi

Takeo Higashi

A polyamide resin-based heat-shrinkable multilayer film having excellent heat shrinkability and strength, as well as a high degree of deep A polyamide resin-based heat-shrinkable multilayer film having excellent heat shrinkability and strength, as well as a high degree of deep drawability as represented a shorter side-basis draw ratio (D/L) in excess of 0.6 between a maximum draw depth (D) and a shorter side length (L) of a mold opening is provided. The multilayer film is characterized by including a surface layer (a) comprising a thermoplastic resin, an intermediate layer (b) comprising a polyamide resin, and a surface layer (c) comprising a sealable resin, wherein (A) the intermediate layer (b) comprises a mixture of an aliphatic polyamide having a melting point of at least 180&#xb0; C., and an amorphous aromatic polyamide comprising a polycondensation product of an aliphatic diamine with is ophthalmic acid and terephthalic acid as main acid components, including 25-45 wt. % of the amorphous aromatic polyamide, and has a thickness exceeding 25% and at most 50% of a total thickness of whole layers, and exhibiting: (B) tensile stresses at an elongation of 100% as measured in a tensile test at 100&#xb0; C., including 3-22 N in at least one of a longitudinal direction (MD) and a transverse direction (TD) and an average of MD and TD values of 3-20N, and (C) a shrinkage in hot water at 90&#xb0; C. of 3 to 20% in each of MD and TD. The film is produced through a process of strictly controlling biaxial stretching ratios and heat-relaxation ratios.

Heat-shrinkable multi-layer film for deep-draw forming, and process for production thereof

A stretch-oriented multilayer film suited for use as a freeze packaging material, a deep drawing packaging material, a vertical pillow packaging material, etc., is provided as a stretch-oriented multilayer film, comprising at least three layers including a surface layer (a) comprising a thermoplastic resin, an intermediate layer (b) comprising a polyamide resin and a surface layer (c) comprising a sealable resin, said multilayer film exhibiting an impact energy of at least 1.5 Joule at a conversion thickness of 50 &#x3bc;m at &#x2212;10&#xb0; C. The multilayer film is produced through an inflation process using water having a large capacity as a cooling and a heating medium and including a combination of a high degree of stretching and a high degree of relaxation heat treatment not exercised heretofore.

Low-temperature impact-resistant polyamide-based stretch-oriented multilayer film

A polyester-surfaced heat-shrinkable multilayer film exhibiting good printability and adaptability to various automatic packaging processes is provided, including an outer surface layer (a) comprising a polyester resin, an intermediate layer (b) comprising a polyamide resin and an inner surface layer (c) comprising a sealable resin. The film exhibits a heat-shrinkable stress at 50&deg; C. of at most 3 MPa both in longitudinal direction and in transverse direction, and a hot water shrinkability at 90&deg; C. of at least 20%.

Heat-shrinkable multilayer film

A polyamide resin-based heat-shrinkable multilayer film is caused to satisfy various properties required of a packaging material, especially a food packaging material, at high levels, and particularly exhibit a highest level of heat-shrinkability. The multilayer film comprises at least three layers including an outer surface layer (a) which comprises a polyester resin or a polyolefin resin; an intermediate layer (b) which comprises a mixture of 85-60 wt. % of an aliphatic polyamide resin, and 15-40 wt. % of an aromatic copolyamide resin which is a copolymer of aliphatic diamine/isophthalic acid and aliphatic diamine/terephthalic acid, and an inner surface layer (c) which essentially comprises a copolymer of ethylene and &agr;-olefin having a density below 0.915. The heat-shrinkable multilayer film has been biaxially stretched and then heat-treated to have hot-water shrinkabilities at 80&deg; C. of at least 30% in each of longitudinal/transverse directions and at least 35% in at least one of longitudinal/transverse directions.

A spiral die for forming a laminate includes an outer die ring, an inner die ring inserted into the outer die ring with a fit clearance therebetween, a plurality (m, a positive integer greater than 1) of spiral grooves each having a gradually decreasing depth disposed between the outer and inner die rings, and distribution paths for distributively introducing melted resin streams of a plurality (n, a positive integer satisfying n&lt;m) of resin species in a prescribed order into said plurality (m) of spiral grooves. The individual resin streams distributed to the spiral grooves proceed along the spiral grooves to gradually overflow the respective spiral grooves and overlie each other in a prescribed order before the individual resin streams form a uniform tubular stream in a die axial direction.

Spiral die and laminate production method using same

A laminate resin film having two major surfaces is constituted by plural resin species. In the laminate, layers of the plural resin species are laminated obliquely to the two major surfaces in at least one section perpendicular to the two major surfaces, and each layer of the plural species of resins is exposed to the two major surfaces. The laminate resin film has equivalent properties in the thickness direction (such as gas-barrier property) as in a conventional laminated film but has properties in the planar extension direction which are remarkably affected by properties (such as low Young's modulus and heat-shrinkability) of a certain component resin layer.

Growing community of inventors

Ibaraki-ken, Japan

Takahisa Ueyama