JP2000001664A - Resin composition for seal and lid material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of exhibiting excellent low temperature sealability and easy peelability, and useful for lid materials exhibiting good sanitariness and flavor impermeability and used for plastic containers, etc., by combining a polyester having a specific melting point with a resin. SOLUTION: This resin composition for seals comprises (A) a polyester having a melting point of <140 deg.C and (B) a resin having a melting point of >=140 deg.C (for example, a polyester, a polyamide, an acrylic resin, a polycarbonate, preferably the polyester) in an A/B weight ratio of 40/60 to 97/3. The composition preferably further contains (C) a polyolefin resin in an amount of 3-25 pts.wt. per 100 pts.wt. of the total amount of the components A and B in addition to the components A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing material, and more particularly, to a sealing material which can be heat-sealed at a low temperature and has an excellent easy peel (easy open) property. A sealing resin composition, a laminate and a lid material suitable for use as a material.

[0002]

2. Description of the Related Art Polypropylene (PP), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (P)
C), tray-shaped or cup-shaped molded articles obtained by thermoforming or injection molding a sheet made of polyvinyl chloride or the like are widely used as containers for foods, beverages, pharmaceuticals, and industrial materials. . In general, when the contents are hermetically packaged in such a plastic container, the contents are filled in the container, and then the lid material and the container are heat-sealed and sealed. At that time, if the heat sealing temperature is high, the plastic container is deformed and the sealing portion becomes thin, so a lid material that can be sealed at low temperature is required. Here, if the sealing strength is too weak, leakage of the contents occurs, or a problem occurs in the storage stability. On the other hand, if the sealing strength is too strong, it is difficult to peel off the lid material by hand, so that the lid material needs to be cut open.

[0003] Further, as a plastic container used for food, polyolefin resins such as PP have been conventionally used in many cases. However, the taste and aroma of the food change due to the adsorption of aroma components of the food. There is a problem that the odor peculiar to the polyolefin resin is generated, thereby losing the original flavor of the food. Therefore, in recent years, food containers having excellent flavor properties, such as PET, PEN, and PC, have been used. However, good lids are not well known for these materials. For example, Japanese Unexamined Patent Publication No. 59-59444 proposes a lid material excellent in easy peeling property by blending a polyethylene resin with polyester, but the flavor property is not good because a large amount of polyethylene resin is used. Even if a small amount of the polyethylene resin was used in order to enhance the flavor, the seal strength was too strong to give an easy peel. Also,
There is also a problem that the compatibility between the two resins is poor, and when extruded to form a film, surging is severe and stable production cannot be achieved. JP-A-59-24667 proposes blending a resin system having poor compatibility in place of the polyolefin resin of the above patent, but still has a problem in terms of stable production. On the other hand, JP-A-63-157
No. 45 proposes to use a polyester having a melting point in the range of 80 to 250 ° C. and a glass transition temperature in the range of 50 to 80 ° C. as a cover material, but the sealing strength is too strong, and peeling by hand is proposed. It was difficult to do. As described above, in a food container having excellent flavor properties such as PET, PEN, and PC, a lid material that secures flavor properties, exhibits sufficient adhesiveness, and also has easy peel properties has not been known. .

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned drawbacks of the prior art and to provide a sealing material which can be sealed at a low temperature and which is excellent in easy peeling property, particularly a lid for a plastic container. An object of the present invention is to provide a sealing material and a lid material used as materials. That is, when used as a sealing resin composition for a lid material, it is a sealing resin composition capable of sealing at a low temperature and achieving an appropriate sealing strength, and a sealing laminate and a lid using the same. Material.

[0005]

Means for Solving the Problems The present inventors have made intensive studies in view of the conventional disadvantages of the lid material for plastic containers, and as a result,
By using a resin having a specific melting point in combination, it has been found that sealing at a low temperature can be performed and a lid material for a plastic container excellent in easy peelability can be obtained, and the present invention has been achieved. That is, the present invention includes (1) a polyester (A) having a melting point of less than 140 ° C. and a resin (B) having a melting point of 140 ° C. or more, wherein (A) / (B)
Is from 40 to 97/3 to 60 (weight ratio). (2) The polyolefin resin is from 3 to 25 parts by weight per 100 parts by weight of the resin composition according to claim 1.
(3) A sealing laminate obtained by laminating the sealing resin composition according to the above (1) or (2) on a base material. (4) A plastic container lid obtained by laminating the seal layer according to (1) or (2) on a substrate.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The most characteristic feature of the present invention is that a polyester (A) having a melting point of less than 140 ° C. is blended with a resin (B) having a melting point of 140 ° C. or more.
The melting point of the polyester (A) used in the present invention is less than 140 ° C. When the melting point is 140 ° C. or higher, it is difficult to seal at a low temperature. The melting point of the polyester (A) is preferably less than 135 ° C., more preferably 130 ° C.
C., most preferably less than 125.degree. The melting point of the resin (B) is 140 ° C. or higher, preferably 15 ° C.
The temperature is 0 ° C. or higher, more preferably 160 ° C. or higher, and most preferably 165 ° C. or higher. When the melting point of the resin (B) is lower than 140 ° C., the sealing strength is increased, and the easy peel property is lacking.

The difference between the melting points of the polyester (A) and the resin (B) is preferably at least 20 ° C, more preferably at least 30 ° C, more preferably at least 40 ° C, most preferably at least 45 ° C. If the difference between the melting points of the polyester (A) and the resin (B) is less than 20 ° C., it will be difficult to achieve both low-temperature sealing properties and easy peel properties. Specifically, a desirable seal strength for exhibiting the easy peel property is 0.5 to 3.0 kgf / 15 mm, and more preferably 0.8 to 2.5 kgf / 15 m.
m, most preferably 1.0 to 2.0 kgf / 15 mm

As the resin (B), for example, polyester,
Known materials such as polyamide, acrylic resin, polycarbonate, cellulose resin, vinyl chloride and the like can be mentioned. In order to exhibit stable easy-peeling properties, the resin (B) is preferably compatible with the resin (A),
It is also required that the resin itself has no odor. For this purpose, the resin (B) is preferably a polyester among the above resins.

The polyester (A) / resin (B) has 4
0 to 97/3 to 60 (weight ratio), preferably 4
5-90 / 10-55, more preferably 50-85 /
15 to 50. The weight ratio of the polyester (A) is 40
If it is less than 97, it is difficult to seal at a low temperature, and if it is more than 97, the sealing strength becomes high and the easy peel property is lacking.

The polybasic acid component constituting the polyester (A) used in the present invention includes terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, decanoic acid, Known substances such as dimer acid, cyclohexanedicarboxylic acid and trimellitic acid can be used.

The polyhydric alcohol component constituting the polyester (A) used in the present invention includes butanediol, ethylene glycol, propylene glycol, 2-methyl-1,3-propanediol, pentanediol and 3-methylpentanediol. , Hexanediol, nonanediol, cyclohexanedimethanol,
Known materials such as polyethylene glycol, polytetramethylene glycol, polypropylene glycol, and trimethylolpropane can be used. When the polyester is used in the resin (B), the same components as those of the polyester (A) can be used as the polybasic acid component and the polyhydric alcohol component.

The reduced viscosity (dl / g) of the polyester resin (A) is preferably from 0.2 to 3.0, more preferably from 0.5 to 2.7, and still more preferably from 0.7 to 2.7. -2.5, most preferably 0.8-2.0. If it is less than 0.2, the adhesive strength may be reduced, and if it is more than 3.0, the compatibility of the composition is reduced and productivity is deteriorated, and stable easy peelability is not exhibited, which is preferable. Absent. The same applies to the reduced viscosity when a polyester is used in the resin (B).

In the present invention, it is also preferable to blend a polyolefin resin in order to provide a more stable easy peel property and a feeling of peeling. When blending a polyolefin resin, the amount of the blend is 3 to 100 parts by weight of the total amount of the polyester resin (A) and the resin (B).
It is 25 parts by weight, preferably 8 to 15 parts by weight. When actually peeling by hand, a blending amount of 3 parts by weight or more is required to obtain a particularly good peeling feeling. However, 2
If the amount exceeds 5 parts by weight, there arises a problem that the seal strength is too weak or the flavor property is poor. Examples of the polyolefin resin include high-density polyethylene, medium-density polyethylene, low-density polyethylene, ionomer, and polypropylene.

The resin of the present invention may contain an inorganic additive and other polymers, if necessary. For example, slip agents include silica, talc, mica, calcium carbonate and the like, and antistatic agents include monoglyceride stearate and polyoxyethylene sorbitanate. Further, a polycarbonate resin or the like can be added in order to reduce the sealing strength and improve the easy peeling property.

The resin composition of the present invention is laminated on a plastic film such as a polyester film or a nylon film, a metal foil such as aluminum, or paper as a substrate, and used as a laminate for sealing.
Particularly, it is most suitable for use as a lid material for a plastic container. As a laminating method, a laminated body can be formed by directly extruding a melt on a substrate, or after forming the resin of the present invention in advance, laminating by heat or laminating using another suitable known adhesive. Can also. The preferred thickness of the seal layer using the resin composition of the present invention is 1 to 100 μm, more preferably 5 to 50 μm, and still more preferably 10 to 3 μm.
0 μm.

[0016]

EXAMPLES Examples are shown below, but the present invention is not limited by these examples. The measured values described in the examples are measured by the following method. Melting point: Measured with a DSC220 model manufactured by Seiko Instruments Inc. 10 mg of the measurement sample was placed in an aluminum pan, sealed by pressing the lid, cooled to −50 ° C. using liquid nitrogen, and then heated to 200 ° C. at a heating rate of 20 ° C./min. In the endothermic curve obtained in the process (the temperature is plotted on the horizontal axis and the amount of heat per unit time is plotted on the vertical axis), the temperature at the intersection of the baseline before the endothermic peak appears and the tangent to the endothermic peak, Invention glass transition temperature T
g.

Seal strength: 30 mmφ manufactured by Ikegai Iron and Steel Co., Ltd.
After kneading using a twin-screw kneader and pelletizing, the mixture was pelletized using a 40 mmφ single-screw extruder manufactured by Nippon Seikosho Co., Ltd.
It was laminated on a μm biaxially stretched PET film to obtain a laminate. The thickness of the seal layer was 30 μm. After the laminate was combined with a 500 μm PEN sheet, heat sealing was performed with a heat seal tester manufactured by Tester Sangyo Co., Ltd. In addition, heat sealing is performed at a temperature of 160 ° C and a pressure of 2 kgf.
/ Cm ² for 2 seconds. The seal strength was measured by using an RTM-100 tensile tester manufactured by Toyo Baldwin Co., Ltd. to measure the T-peeling adhesive strength at a tensile speed of 300 mm / min. In order to evaluate the peeling sensation, the seal strength sample was peeled off by a human hand at a constant speed and force as much as possible, and the peeling sensation at this time was evaluated. Those that can be easily peeled off at a constant speed have good peeling feeling (、, especially good ones), and those that are hard to peel off at a constant speed, feel caught halfway, and stop peeling are bad (x). did. Further, in the overall judgment, taking into account the peeling adhesive force and the peeling feeling, 良好 was given for good samples, ◎ was given for particularly good products, and × was given for bad products.

Reduced viscosity: 0.1 g of polyester in phenol / tetrachloroethane (weight ratio 6/4) mixed solvent 2
It was dissolved in 5 cc and measured at 30 ° C. using an Ubbelohde viscometer.

Production Example of Polyester (I) In a reaction vessel equipped with a stirrer, a thermometer and a distilling cooler, 2440 parts by weight of terephthalic acid, 2970 parts by weight of sebacic acid, 5290 parts by weight of butanediol, and 7 parts by weight of tetrabutyl titanate Then, 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 to 220 to 250 ° C., and the pressure inside the reaction vessel was gradually reduced, and the pressure was increased to 245 ° C. and 5 Torr over 60 minutes. Then, a polycondensation reaction was further performed for 60 minutes at 1 Torr or less to obtain a polyester (I). Polyester (I)
As a result of NMR analysis, was a crystalline resin having a composition of 50 mol% of terephthalic acid, 50 mol% of sebacic acid and 100 mol% of butanediol, a melting point of 117 ° C. and a reduced viscosity of 1.2 dl / g.

Polyesters (II), (III) and (IV)
Was synthesized by the same method as for polyester (I). Polyester (II) has a composition of terephthalic acid 65 mol%, isophthalic acid 10 mol%, adipic acid 25 mol%, and butanediol 100 mol%.
It was a crystalline resin having a reduced viscosity of 0.9 dl / g. Polyester (III) has a composition of 65 mol% of terephthalic acid, 35 mol% of isophthalic acid, 83.4 mol% of butanediol, and 16.6 mol% of polytetramethylene glycol.
It was a crystalline resin having a melting point of 123 ° C. and a reduced viscosity of 1.8 dl / g. Polyester (IV) is a crystalline resin having a composition of 70 mol% of terephthalic acid, 10 mol% of isophthalic acid, 20 mol% of sebacic acid and 100 mol% of butanediol, having a melting point of 171 ° C. and a reduced viscosity of 0.8 dl / g. Met.

[0021]

[Table 1]

[0022]

As described above, according to the present invention, it is possible to provide a seal material which is excellent as a lid material for a plastic container and which has excellent easy peeling properties and also has hygiene properties and flavor properties which are characteristics of polyester. it can.

Continued on the front page F-term (reference) 3E067 AB81 BA07A BA10A BB14A BB25A BC07A CA24 EA06 EA13 GB15 GD08 4H017 AA04 AB07 AB13 AC02 AC16 AD06 AE04 4J002 AB01X BB033 BB123 BB233 BD03X BG00X CF00X CF00X CG00 00

Claims (4)

[Claims] 1. A polyester (A) having a melting point of less than 140 ° C. and a resin (B) having a melting point of 140 ° C. or more,
(A) / (B) is 40 to 97/3 to 60 (weight ratio), a sealing resin composition. 2. A sealing resin composition comprising 3 to 25 parts by weight of a polyolefin resin per 100 parts by weight of the resin composition according to claim 1. 3. A sealing laminate obtained by laminating the sealing resin composition according to claim 1 on a substrate. 4. A lid material for a plastic container obtained by laminating the resin composition for sealing according to claim 1 or 2 on a base material.