JPH11349708A - Easy-peel sealing material and lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an easy-peel sealing material enabling the heat-sealing of a plastic plate and plastic vessel at a low temperature and having excellent retort resistance by using a crystalline polyester having respectively specific glass transition temperature and melting point. SOLUTION: The objective material is composed of a polyester resin composition composed mainly of a crystalline polyester having a glass transition temperature of <=0 deg.C and a melting point of 120-200 deg.C. The composition is preferably composed of (A) 97-80 wt.% of the crystalline polyester and (B) 3-20 wt.% of a polyolefin resin (e.g. polyethylene). The composition may be incorporated with an additive, e.g. a slipping agent such as silica.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seal material for an easy peel, particularly a plastic plate or a plastic container,
In particular, crystallized polyethylene terephthalate (hereinafter C-
Easy peel seal material that can be easily peeled off when peeled off while being able to be heat-sealed at a low temperature between a plate or a C-PET container and may be abbreviated as PET). And a lid material obtained by laminating the sealing material for easy peel and a base material, and heat-sealing with a plastic plate or a plastic container.

[0002]

2. Description of the Related Art A tray-shaped or cup-shaped molded product obtained by thermoforming or injection molding a plastic sheet such as polypropylene, polyethylene terephthalate, polystyrene, polycarbonate, polyvinyl chloride, etc. is a container for food and beverages. Widely used as. Generally, when the contents are hermetically packaged in such a plastic container, the contents are filled into the container, and then the lid material and the plastic container are heat-sealed and sealed. At this time, if the heat sealing temperature is high, the plastic container may be deformed, or the heat sealing portion may become thin and the contents may leak. Therefore, a sealing material capable of heat sealing at a low temperature is required. Further, if the sealing strength is too strong, it is difficult to peel off the lid by hand, so that the lid needs to be cut open. That is, it is necessary for the sealing material to be able to seal at a low temperature and to maintain an appropriate sealing strength. Specifically, the seal strength is 1-2 kgf / 15
mm.

[0003] As plastics used for food containers, polyolefins such as polypropylene have been widely used in the past. However, the taste and aroma of foods may change due to adsorption of aroma components of the foods. There is a problem that odor may be generated and the original flavor of food is lost. Therefore, recently, there has been a movement to use a food container made of a so-called good-flavor plastic such as polyethylene terephthalate to improve this point.

Recently, high-temperature filling, high-temperature boiling, and retort treatment have been increasing for the purpose of storing food at room temperature for a long period of time, and a container having heat resistance has been demanded. C-PET has attracted attention as a material that can withstand retort sterilization and has excellent flavor properties. However, even if you try to heat seal a C-PET container with a sealing material known so far,
At low temperatures, C-PET is not softened at all, and thus has poor adhesion. Even if the sealing temperature is increased to near the melting point of C-PET and heat-sealed, the plastic container is deformed and is not practically usable. Further, if the heat resistance of the seal layer itself is insufficient, there is a problem that whitening, deformation, leakage of contents, and the like occur during sterilization of the retort.
For that purpose, a method of inserting a lid material molded to fit the container or circulating the container itself in a bag is used, but since retort sterilization after filling the contents is impossible, In fact, it was not very popular.

Japanese Patent Application Laid-Open No. 60-180833 discloses a resin composition obtained by blending a polyethylene terephthalate resin, a polybutylene terephthalate resin and a polyolefin resin in a polyester container. Although it is proposed to use as a sealing material, it is also described that heat sealing is difficult unless the polyethylene terephthalate of the container is non-oriented (amorphous). Japanese Patent Application Laid-Open No. 4-18268 proposes a sealing material using two types of polyester resins, one of which is applied to the entire surface and the other is applied to a portion such as a mesh, for example. From the viewpoint of performance, such as retort resistance, it was difficult to put into practical use. Further, JP-A-59-594
No. 44 proposes a lid material excellent in easy peeling property by blending a polyester resin with a polyester, but the flavor property is not good because a large amount of the polyethylene resin is used. In addition, the resin (high T
g amorphous), it was not possible to seal at all with C-PET.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the conventional easy peel seal material, and uses a crystalline polyester having a specific glass transition temperature and a specific melting point to produce a plastic plate and a plastic. A sealing material which can be heat-sealed at a low temperature to a container, particularly a C-PET plate or a C-PET container, which has been difficult to heat-seal, and which is excellent in retort resistance and easy peelability; It is intended to provide a lid material.

[0007]

In order to achieve the above object, an easy peel seal material of the present invention comprises a polyester mainly composed of a crystalline polyester having a glass transition temperature of 0 ° C. or less and a melting point of 120 to 200 ° C. It is characterized by being composed of a resin composition.

[0008] The easy peel seal material of the present invention having the above-described structure is excellent in both low temperature heat sealability, retort resistance and easy peelability.

In this case, the polyester resin composition may be a resin composition comprising 97 to 80% by weight of a crystalline polyester and 3 to 20% by weight of a polyolefin resin.

[0010] The easy peel lid material of the present invention is characterized in that the above easy peel seal material is laminated on a base material.

The easy-peel lid material of the present invention having the above-described structure has excellent strength and excellent low-temperature heat sealability, retort resistance and easy-peel properties.

[0012] In this case, the above-mentioned easy peel lid material can be heat-sealed to a polyester product.

[0013] In this case, the polyester is made of crystallized polyethylene terephthalate (C-PE).
T).

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of an easy peel seal material and a lid material according to the present invention will be described in detail.

The crystalline polyester which is the main component of the polyester resin composition used in the present invention has a glass transition temperature of 0 ° C. or lower, preferably -5 ° C. or lower. When the glass transition temperature exceeds 0 ° C., the volumetric shrinkage of the crystalline polyester during crystallization is large, and the adhesion to the crystallized polyethylene terephthalate is significantly reduced.

The melting point of the crystalline polyester used for the easy peel seal material of the present invention is from 120 to 200 ° C., preferably from 120 to 180 ° C. Melting point is 1
If the temperature is lower than 20 ° C., whitening or deformation of the adhesive layer occurs during retort and the appearance is deteriorated, and the seal strength is significantly reduced. If the temperature exceeds 200 ° C., the sealing temperature needs to be increased, and C-PET is softened and deformed. Appearance becomes poor. The reduced viscosity (ηsp / c) of the crystalline polyester is usually preferably about 0.5 to 2.0 from the viewpoint of film formability.

The polyvalent carboxylic acid component constituting the crystalline polyester used in the easy peel seal material of the present invention includes terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, Known ones such as decanoic acid, dimer acid, cyclohexanedicarboxylic acid and trimellitic acid can be used. The polyhydric alcohol component includes ethylene glycol, propylene glycol, butanediol, 2-methyl-1,3-propanediol, pentanediol, 3-methylpentanediol, hexanediol, nonanediol, cyclohexanedimethanol,
Polyethylene glycol, polypropylene glycol,
Polytetramethylene glycol, trimethylolpropane and the like can be used.

The main component of the polyester resin composition used for the easy peel seal material of the present invention is a crystalline polyester, but various additives can be added as needed. For example, slip agents include silica, talc, mica, calcium carbonate and the like, and antistatic agents include monoglyceride stearate and polyoxyethylene sorbitanate. In addition, a polyolefin-based resin, polyamide, polycarbonate, or the like can be partially contained within a range that does not significantly change the characteristics.

In particular, a polyolefin resin may be contained in addition to the main component crystalline polyester in order to appropriately adjust the heat sealing strength of the easy peel seal material to improve the easy peel property. When a polyolefin resin is blended with the crystalline polyester used in the present invention, 3 to 20% by weight, preferably 8 to 2% by weight.
0% by weight. A peel strength of 1-2 within the above range
By adjusting to kgf / 15 mm, an easy peel seal material can be obtained. When actually peeling by hand, it is preferable to blend 3% by weight or more of a polyolefin resin in order to obtain particularly excellent easy peeling property, that is, a good feeling of peeling. However, if the blend amount exceeds 20% by weight, the sealing strength tends to be weak, and furthermore, the flavor property is poor, so that problems such as resin odor and adsorption of the contents of the container are caused. As the polyolefin resin to be added, polyethylene, polypropylene, polybutene, poly-4-methylpentene-1, ionomer, ethylene propylene copolymer, ethylene butene copolymer,
A propylene / butene copolymer can be used.

The following method is used to measure the sealing strength of the easy peel seal material used in the present invention. After laminating a sealing material layer on the corona discharge treated surface of a 50 μm biaxially stretched polyethylene terephthalate film (E1501 manufactured by Toyobo Co., Ltd.), 500 μm
m-crystallized C-PET (C5 manufactured by Toyobo Co., Ltd.)
605Z1R) (heat seal tester TP-701-B manufactured by Tester Sangyo Co., Ltd.) 140 ° C. × 2 kgf
After bonding under the condition of / cm ² × 2 seconds, T-peeling is performed at a speed of 300 mm / min using a tensile tester. The value at which the easy-peeling property is good as the seal strength at this time is 1 to 2 kgf / 15 mm, and preferably 1.3 to 2 kgf / 15 mm.
It is in the range of 1.8 kgf / 15 mm. If the seal strength exceeds 2 kgf / 15 mm, it is difficult to open the seal especially for a person or a child without power, and it is necessary to cut the seal with a knife or the like. In some cases, the biaxially stretched polyethylene terephthalate film itself, which is the base material, is broken, and the lid may be broken. On the other hand, the seal strength is 1 kgf
If it is less than / 15 mm, the lid may be opened carelessly due to an increase in internal pressure during retort or vibration during transportation.

The easy-peel sealing material containing the crystalline polyester as a main component of the present invention can be directly melt-extruded onto a substrate, for example, a plastic film such as a polyethylene terephthalate film, a metal foil such as aluminum, or paper. It is also possible to form a laminated body, or after forming a crystalline polyester used in the easy peel seal material of the present invention into a film in advance, and using another suitable known adhesive to laminate the above-mentioned base material You can do things.

The laminate containing the easy peel seal material of the present invention can be used for general heat sealing, but is particularly suitable as an easy peel lid material for heat sealing polyester products such as plastic plates or plastic containers. is there. Among them, polyester, especially C-PET plate or C-PE, which was difficult to seal conventionally
Most suitable as a lid material for sealing the T container. The thickness of the easy peel seal material of the present invention can be arbitrarily determined depending on the application, but is usually about 3 to 50 to μm. In addition, the thickness of the lid material can be arbitrarily determined depending on the application,
Usually, it is about 20 to 150 μm.

The crystallized polyethylene terephthalate (C-PET) used in the present invention refers to terephthalic acid as a polyvalent carboxylic acid component, and partially isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, succinic acid, and adipine. Acid, azelaic acid, sebacic acid, decanoic acid, dimer acid, cyclohexanedicarboxylic acid, trimellitic acid, etc., if necessary.The polyhydric alcohol component is mainly composed of ethylene glycol, and the other is partially propylene glycol. , Butanediol, 2-methyl-1,3-propanediol, pentanediol, 3-methylpentanediol, hexanediol, nonanediol, cyclohexanedimethanol,
Polyethylene glycol, polypropylene glycol,
If necessary, polytetramethylene glycol, trimethylolpropane and the like can be contained. Furthermore, C-PE
A crystal nucleus material can be added to T as needed, and examples thereof include inorganic substances such as talc and mica, and organic substances such as polyolefin and polyamide.

[0024]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto. The measured values described in the examples are measured by the following method.

Glass transition temperature, melting point: Measured with a DSC 220 model manufactured by Seiko Denshi Kogyo KK at a heating rate of 20 ° C./min. Put 10mg of measurement sample in aluminum pan,
The lid was pressed down, sealed and measured.

Seal strength: A 40 μm sealing material layer is laminated on 50 μm biaxially stretched PET, then combined with a 300 μm crystallized C-PET, and then using a heat seal tester manufactured by Tester Sangyo Co., Ltd. Heat sealing was performed. In addition, heat sealing is performed at a temperature of 140 ° C. and a pressure of 2 kg.
The test was performed at f / cm ² for 2 seconds. The seal strength was measured using a Toyo Baldwin RTM-100 tensile tester.
The T-peel adhesion was measured at a pulling speed of 0 mm / min. Those with a seal strength of 1 to 2 kgf / 15 mm were judged as good, and those with other seal strengths were judged as bad.

Retort test: After performing a retort treatment at 120 ° C. for 30 minutes, changes in the appearance (deformation, whitening) of the seal layer were confirmed.

Reduced viscosity: 0.1 g of polyester mixed solvent 2 with phenol-no-tetrachloroethane (weight ratio 6/4)
The sample was dissolved in 5 cc and measured at 30 ° C. using an Ubbelohde viscometer.

Production Example of Crystalline Polyester (I) 2590 parts by weight of terephthalic acid, 2790 parts by weight of sebacic acid, 5290 parts by weight of butanediol, 5290 parts by weight of tetrabutyl titanate are placed in a reaction vessel equipped with a stirrer, a thermometer and a condenser for distillation. 7 parts by weight were added, and an esterification reaction was performed at 170 to 220 ° C. for 2 hours. After the completion of the esterification reaction, the temperature of the reaction system was raised from 220 ° C. to 255 ° C., while the inside of the system was gradually reduced in pressure, and was heated at 255 ° C. and 5 Torr for 60 minutes.
And Then, a polycondensation reaction was further performed at 1 Torr or less for 55 minutes to obtain a white crystalline polyester (I).

As a result of NMR analysis of the crystalline polyester (I), the dicarboxylic acid component contained 53 mol% of terephthalic acid,
Sebacic acid had a composition of 47 mol%, and the diol component had a composition of 100 mol% of butanediol. The glass transition temperature is -36 ° C, the melting point is 122 ° C, and the reduced viscosity (ηsp /
c) = 120 crystalline resin.

The crystallized polyesters (II) to (IV) were synthesized by the same method as for the crystalline polyester (I).
The respective values are shown in Table 1 (the numerical values are mol% in the resin).

The formulations in Table 2 are by weight (%). still,
Himilan 1650 manufactured by DuPont-Mitsui Polychemicals Co., Ltd. was used as the ionomer, and Noblen W101 manufactured by Sumitomo Chemical Co., Ltd. was used as the polypropylene. Kneading is performed using a 30 mmφ biaxial kneading machine manufactured by Ikegai Iron Works Co., Ltd., and after pelletizing, 40 m manufactured by NSK Ltd.
An evaluation sample was obtained by extruding and laminating on a substrate made of a 50 μm biaxially stretched PET film using an mφ uniaxial extruder. The polyester alone was directly extruded and laminated.

[0033]

[Table 1]

[0034]

[Table 2]

[0035]

According to the easy peel seal material of the present invention, both low temperature heat sealability, retort resistance and easy peelability are excellent. Further, the easy peel lid material has excellent strength, and also has excellent low-temperature heat sealability, retort resistance, and easy peel properties.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁶ Identification code FI C09J 167/02 C09J 167/02 C08L 67:02

Claims (5)

[Claims] 1. A glass transition temperature of 0 ° C. or less and a melting point of 12
An easy peel seal material comprising a polyester resin composition containing a crystalline polyester at 0 to 200 ° C. as a main component. 2. A polyester resin composition comprising 97-80% by weight of a crystalline polyester and polyolefin resin 3
The easy peel seal material according to claim 1, which is a composition comprising -20% by weight. 3. An easy-peel lid material comprising the easy-peel seal material according to claim 1 laminated on a base material. 4. The easy peel lid material according to claim 3, which is heat-sealed to a polyester product. 5. The easy peel lid material according to claim 4, wherein the polyester is crystallized polyethylene terephthalate (C-PET).