JPH02279782A - Heat-sealable coating material for adhering styrene resin - Google Patents

Abstract

PURPOSE:To obtain the subject material exhibiting excellent heat-sealing properties to a styrene resin container when a covering material such as a metal foil is coated with this coating and forming a heat-sealing resin layer peelable at an interface between the heat-sealing resin layer and the container or an interface between said resin layer and the covering material when the covering is peeled off by adding a specified amt. of an inorg. filler to an acrylic resin soln. CONSTITUTION:The subject coating material is prepared by adding 2 to 25 pts.wt. inorg. filler (e.g. talc powder) based on 100 pts.wt. nonvolatile component of an acrylic resin soln. (e.g. n-butyl acrylate-methyl methacrylate-acrylic acid copolymer soln. in ethyl acetate and toluene) to said soln.

Description

[Detailed description of the invention] (Industrial usage amount ￥f) The present invention provides a thermoplastic resin layer that is applied to a base material such as a plastic film or metal foil and exhibits good heat sealability against styrene resin. More specifically regarding the coating that can be formed,
In particular, the object of the present invention is to provide a heat-sealable coating material that can form a heat-sealable resin layer exhibiting high heat-sealing strength when applied to aluminum foil as a lid material for a styrene-based resin packaging container.

(Prior Art) Hitherto, it has been widely practiced to seal the lid of a plastic container using a sealing hot plate (heat-seal bar), high frequency waves, ultrasonic waves, or the like. The general form of the lid material is metal foil such as aluminum foil, paper, heat-resistant plastic film, or metal vapor-deposited paper or film as the base material, with thermoplastic resin on one side. A heat-sealable resin layer is provided as a basic component.

In addition, various variations have been made in order to improve heat sealability, such as providing a polyethylene resin layer as a buffer layer between the heat sealable resin layer and the base material. The other side is generally printed with letters and designs, and to protect it, it is coated with a heat-resistant transparent resin varnish or laminated with a heat-resistant plastic film.

(Problems to be solved by the invention) So-called seal packs, which use containers whose main component is styrene resin among plastics and seal the opening with a lid, are widely used in various fields, mainly in the food packaging field. However, the lid material for these is often aluminum foil coated with a heat-sealing adhesive.

Various resin-based materials are being considered as the main component of the coating material for forming the heat-sealable resin layer of the lid material for styrene-based resin containers, but among these, acrylic resin-based materials are relatively popular. It is evaluated as having good heat sealability.

However, the reality is that the heat sealing strength is not necessarily sufficient, and improvements are required.

(Means for Solving the Problem) As a result of studying various resin systems and blend systems thereof, the present inventors found that the heat-sealable resin layer of the lid material for styrene resin containers, which is the object of the present invention, It has been found that acrylic resins are suitable as the main component of the coating material for forming the coating material, as has been conventionally recognized. Furthermore, by using known means such as blending other types of resins with the acrylic resin or adding adhesion promoters, results were obtained in which the heat sealing strength was slightly improved in some cases.

However, when the heat-sealing strength improves, there is a tendency for cohesive failure to occur in the heat-sealing resin layer of the lid when peeling off the lid that has been heat-sealed to a styrene-based resin container, and the destroyed resin layer contaminates the contents. In addition, fragments of the resin layer remaining attached to the edge of the container, so-called so-called ridges, cause discomfort when the container is used as tableware, which poses a practical problem.

The present inventors solved the above-mentioned problems and created a lid material that has a sufficiently high heat-sealing strength for a styrene-based resin container, and that can be heat-sealed without causing destruction of the heat-sealing resin layer when the lid is peeled off. To obtain a heat-sealable coating that forms a heat-sealable resin layer that can be peeled off at the interface between the thermoplastic resin layer and the container or the interface between the heat-sealable resin layer and the aluminum foil that is the base material of the lid material. As a result of repeated research, we found that by adding 2 to 25 parts of an inorganic filler to 100 parts of the nonvolatile content of the acrylic resin solution of a heat-sealable coating material whose main component is an acrylic resin solution, it is possible to create a heat sealable coating material made of styrene resin. The heat sealing strength of the container lid material is 1.0 k at a heat sealing temperature of around 150°C.
It has been discovered that a heat-sealable coating material that always exhibits a strength of g/15m+m or more, does not cause cohesive failure when a heat-sealed lid material is peeled off, and can form a heat-sealable resin layer that peels off at the interface. The present invention has been achieved.

The acrylic resin solution used in the present invention can be obtained by a known manufacturing method. That is, the acrylic resin produced by any method such as suspension polymerization method, emulsion polymerization method, bulk type method, etc. is dissolved in an appropriate organic solvent, or the acrylic resin is formed in an appropriate organic solvent. An acrylic resin solution or the like obtained by solution polymerizing component monomers is used.

The monomer that is a constituent component of acrylic resin can be any known monomer that is generally used in the production of acrylic resin. A typical example is C1-18 alkyl (meth)acrylate, but other monomers can be used. Styrene as a monomer,
Copolymerizable hard monomers such as acrylonitrile and vinyl acetate with a homopolymer secondary transition point of about 20°C or higher;
Monomers having functional groups other than meth>acrylic acid, such as polymerizable carboxylic acids such as itaconic acid, crotonic acid, and fumaric acid, methylol (meth)acrylamide alkyl ethers, hydroxyalkyl (meth)acrylates,
Examples include glycidyl (meth)acrylates.

There are no particular restrictions on the acrylic resin, but those with too low a softening point should be avoided as they may cause blocking.

As the inorganic filler, known ones used in paints and printing inks can be used, but among them, for example, silicic anhydride, talc, clay, precipitated sulfuric acid barum,
External pigments such as alumina, calcium carbonate, and zinc white are preferred because of their transparency, but other colored pigments may also be used if necessary.

(Functions and Effects) The proportion of the inorganic filler used in the heat-sealable coating for styrene resin adhesive of the present invention is suitably in the range of 2 to 25 parts per 100 parts of nonvolatile content of the acrylic resin solution.

If the amount of inorganic filler added is less than 2 parts per 100 parts of non-volatile content of the acrylic resin solution, the heat sealing strength will not be sufficiently improved, and A2 failure will occur when peeling off after heat sealing the styrene resin. The tendency for this to occur is also not improved. Also, 2
If the amount exceeds 5 parts, the heat sealing temperature will rise and heat sealing will not be performed sufficiently, resulting in a decrease in heat sealing strength.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

Reference example (manufacturing example of acrylic resin solution A) The following compositions A, B, C, D, and E were placed in a 1-liter four-bottle flask equipped with a stirrer, reflux condenser, dropping funnel, and inert gas introduction tube. and F are charged, stirring is started, and nitrogen gas is smoothly introduced from the inert gas introduction tube to replace the atmosphere.

A, n-butyl acrylate 94 OgD
Methyl methacrylate 300.0gC acrylic acid
6. OgD ethyl acetate
320. OgD Dollar All 24
0. OgD Azobisisobutyronitrile 24g Next, heating was started and the internal temperature of the flask was raised to 70°C in 30 minutes.
temperature and then held at 70°C for 2 hours. Subsequently, the temperature was raised to 80°C and held for 5 hours, then raised to 90°C for 3 hours, 20.0 g of ethyl acetate and 20.0 g of doluol were added, and the acrylic resin solution was cooled. I got an A.

The nonvolatile content was 405% and the viscosity was 10 voids.

(Production example of acrylic resin solution B) Add the following compositions A, B, C, E, and F to the same flask as in the production example of acrylic resin solution A, start stirring, and cool the atmosphere inside the flask. Replace with nitrogen gas.

A Methyl methacrylate 260. OgD Styrene 31.0gC Methacrylic acid
9. OgD benzoyl peroxide
3.6gE Methyl ethyl ketone 30
0.0g.

F Doror 2o○, Og.

Heat to raise the internal temperature of the flask to 75°C 9. Immediately add 51.8 g of solution 78 in which 36 g of benzoyl peroxide 4 was dissolved in 100.0 g of doluol prepared separately from the dropping funnel. Start the reaction and heat to 75°C for 2
After holding for an hour, the temperature was raised to 80°C and held for 10 hours to complete the reaction. After the completion of 9 reactions, the remaining 51.8 g of the doluol solution of benzoyl peroxide was added evenly over a period of 5 hours from the time when the temperature reached 80°C.
Methyl ethyl ketone 100. Og is added and cooled to obtain an acrylic resin varnish.

The acrylic resin varnish was taken out, and a separately prepared fS vinyl chloride-vinyl acetate copolymer (vinylite VMCH, manufactured by UCC, USA, dissolved in 30 parts of a 1:1 mixed solvent of ethyl acetate/methyl ethyl ketone) was added at a shallow frequency of 130 Hz. By mixing, acrylic resin solution B was obtained.

The nonvolatile content was 29.8%, and the viscosity was 11.3 voids.

Example 1 300 g of acrylic resin solution A of the reference example was weighed out, and 2 g of talc powder (manufactured by Nippon Talc Co., Ltd.; Micro Ace L-1) was weighed out.
A heat-sealable coating was obtained by adding 7.6 g and dispersing for 20 minutes using an 800 cc batch tabletop sand mill.

This heat-sealable coating was applied to a soft aluminum foil with a thickness of 50 μm to a dry coating amount of approximately 5 g/ro”, and dried by heating for 10 seconds in a drying oven at an ambient temperature of 180°C. A sealing resin layer was formed and a coated aluminum foil was prepared.

Next, the obtained coated aluminum foil was applied to a high impact polystyrene (1-(I P S ) sheet (manufactured by Asahi Dow Co., Ltd., Styron #470) with a thickness of 0.5 mm at a heat sealing temperature of 130°C. Heat sealing was performed at 150° C. and 170° C. under conditions of a pressure of 3.0 kg/cm 2 and a crimping time of 10 seconds to prepare a sample for heat sealing strength measurement.

A 180 degree release test (pulling speed 200 cm/min) was performed on the heat sealing strength measurement sample' using an Autograph (manufactured by Shimadzu Corporation), and the heat sealing temperature was 130°C1.
Strength at 150°C and 170°C: 1.177.1,180 and 1.220g, /15 respectively
I got the value.

Moreover, peeling occurred between the aluminum foil and the heat-sealable resin layer, and there was no tendency at all to cause cohesive failure and leave edge residue.

It is said that it is practically sufficient if a value of 1.00g,/15wm or more is obtained as a heat sealing strength at least at a heat sealing temperature of around 150°C, so the above value should be satisfied.

Example 2 Exactly the same operation as in Example 1 was performed except that the amount of talc powder was changed to 6.0 g, and as a result of a 180 degree peel test on a sample for heat sealing strength measurement, the heat sealing temperature was 13.
1. for 0°C, 150°C and 170°C, respectively.
047.1.173 and 1, 310 g, /15m
The strength was obtained.

Moreover, peeling occurred between the aluminum foil and the heat-sealable resin layer, and there was no tendency at all to cause cohesive failure and leave edge residue.

Comparative Example 1 The same operation as in Example 1 was performed except that 36.0 g of talc powder was added, exceeding the upper limit of the range of addition amount of the present invention. The results of a 180 degree peel test on samples for heat sealing strength measurement showed that all peeling occurred between the aluminum foil and the heat sealable resin layer, and no cohesive failure occurred, but the heat sealing temperature was 130"C1150 °C and 1
The strength at 70°C is 447.568 and 6, respectively.
A value of only 60g/15m was obtained.

Comparative Example 2 The same operation as in Example 1 was carried out without stirring the talc powder.

The results of the 180 degree peel test on the samples for heat sealing strength measurement showed that when the heat sealing temperature was 130°C, 5150°C, and 170°C, the strengths were only 693.840 and 943 g/15°C, respectively. Moreover, the peeling occurred due to cohesive failure within the heat-sealable resin layer, leaving edge residue on the peeled surface.

Example 3 In Example 1, 8400 g of the acrylic resin solution of the reference example was used instead of acrylic resin solution A, and 6.0 g of silica powder (manufactured by Fuji Davison Co., Ltd.; Cyroid #24) was added instead of talc powder. A sample for measuring heat sealing strength was prepared in the same manner as in Example 1. 9 A sample for measuring heat sealing strength was prepared in the same manner as in Example 1.
An 80 degree peel test was conducted, but the heat sealing temperature was 130℃, 15
Heat seal strength at 0°C and 170°C: 1,251.1,366 and 1.420 g/1, respectively
A value of 5 yen was obtained.

Further, peeling occurred between the aluminum foil and the heat sealable resin layer.

Example 4 A sample for heat sealing strength measurement was obtained in the same manner as in Example 3 except that 24.0 g of precipitated barium sulfate was used instead of silica powder as the inorganic filler, and a 180 degree peel test was conducted. The strength for sealing temperatures of 130°C, 150°C and 170°C is 1 and 10, respectively.
Values of 5.1,237 and 1,340 g,/15m were obtained.

The peeled surface was between the aluminum foil and the heat-sealing resin layer, and no edge residue was observed.

Example 5 A sample for heat sealing strength measurement was obtained in exactly the same manner as in Example 3 except that 12.0 g of Zinc White No. 2 was used instead of Shitsukawa) powder as the inorganic filler.

In the 180 degree peel test, the strength was 1.31 at heat sealing temperatures of 130°C, 1150°C, and 170°C, respectively.
Values of 0.1.384 and 1.417 g,/15mm were obtained.

Further, the peeled surface was between the aluminum foil and the heat-sealable resin layer, and no cohesive failure of the heat-sealable resin layer was observed.

Leader Co., Ltd.

Claims (1)

[Claims] A heat-sealable coating for adhesion to styrenic resins, which is made by adding 2 to 25 parts of an inorganic filler to 100 parts (parts by weight, same hereinafter) of non-volatile content of an acrylic resin solution.