JP2002088309A - Heat-sealing coating agent, and heat-sealable multilayer structure coated therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a heat-sealing coating agent excellent in heat-sealing effect, appearance, surface resistivity (both at high and low humidities), solvent resistance and water resistance, and suitable for packaging materials of good workability, and to provide a heat-sealable multilayer structure coated with the coating agent. SOLUTION: This heat-sealing coating agent is characterized in that the coating film made therefrom has a low-humidity surface resistivity of <=1012 Ω(determined at 30 deg.C, 30%RH and an applied voltage of 560 V). The heat- sealable multilayer structure coated with the agent is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat-sealing coating agent and a heat-sealing coating material having a low humidity surface resistivity of 10 ¹² Ω or less when a coating film is formed. The present invention relates to a heat-sealable multilayer structure including a heat-sealable layer obtained from an agent. This is excellent in packaging workability under low humidity. Further, in the present invention, the heat-sealing coating agent comprises an aqueous resin and a water-retaining and moisture-retaining additive such as urea. This is because harmful gases such as hydrogen halide and dioxin are not generated when incinerated as waste, in contrast to heat-sealable films processed with conventional halogen-containing resins (such as vinylidene chloride resin). It is characteristic.

[0002]

2. Description of the Related Art Various attempts have been made to impart heat sealability to packaging materials and the like, and the necessity has increased as packaging has been simplified. For example,
Japanese Patent Publication No. 63-3883 discloses a heat-sealing property imparting agent using a vinylidene chloride-methyl methacrylate copolymer, which contains chlorine and is difficult to dispose of as waste. There is a problem that hydrogen halide or dioxin may be generated. Also, Japanese Patent Application Laid-Open No. 50-150783 discloses a film in which an acrylonitrile copolymer is laminated, but acrylonitrile has poor heat yellowing resistance, and when used as a packaging material, yellowish during storage. There is a problem that the appearance deteriorates and the commercial value is reduced. Japanese Patent Application Laid-Open No. 57-137339 discloses an aqueous dispersion composition obtained by modifying a copolymer of ethylene, an α, β-unsaturated carboxylic acid and a metal salt of an α, β-unsaturated carboxylic acid with an aqueous dispersion composition. Although excellent in high-temperature heat sealability, low-temperature heat sealability is insufficient. Also, ethylene, α, β
-Use of a modified product of an unsaturated carboxylic acid and an α, β-unsaturated carboxylic acid metal salt copolymer modified with styrene and a (meth) acrylate ester has satisfactory heat sealing properties, Poor quality and yellowing during storage. Furthermore, in the case of these ethylene, α, β-unsaturated carboxylic acids and modified products thereof, the film has a high surface resistivity under low humidity such as in winter, so that the film is stuck and the packaging workability is increased. There are also problems that get worse.

[0003]

The present invention solves all of the above problems, has sufficient heat sealing properties at low temperatures, has weather resistance,
A heat-sealing coating agent that has excellent water resistance, solvent resistance, and workability (good surface specific resistance under low humidity) and does not generate toxic gases such as hydrogen halide and dioxin when incinerated. And packaging materials.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, completed the present invention. That is, the present invention provides: [1] a heat-sealable coating characterized by forming a coating film having a low humidity surface resistivity (measured at 30 ° C., 30% RH, applied voltage of 560 V) of 10 ¹² Ω or less. Agent. [2] The description of [1], wherein (a) an aqueous resin and (b) at least one additive selected from urea, polyethylene glycols, silica compounds, celluloses, and caseins are mixed. Heat-sealable coating agent. [3] The heat-sealing coating agent according to [2], wherein the aqueous resin is a water-dispersed resin. [4] At least part of two layers of (I) a layer composed of a base material and (II) a heat seal layer composed of the heat sealable coating agent according to any one of [1] to [3]. A heat-sealing multilayer structure having two or more layers. [5] The heat-sealing multilayer structure according to [4], wherein the substrate is a polyolefin film.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The contents of the present invention will be described in detail below. The heat-sealable coating agent of the present invention has a low-moisture surface resistivity (30 ° C., 30
% RH, measured at an applied voltage of 560 V) is 10 ¹² Ω or less. In the present invention, the low humidity surface resistivity is 3
In a constant-temperature and constant-humidity box of 0 ° C. and 30% RH, a commercially available surface resistance measuring instrument, for example, a digital ultra-high resistance / micro ammeter R8340A manufactured by Advantest Co., Ltd. is allowed to stand for a certain period of time and measured at an applied voltage of 560 V. is there. 10 ¹² Ω
The following can be considered a practical level.

The heat-sealing coating agent of the present invention comprises (a) an aqueous resin and (b) at least one additive selected from urea, polyethylene glycols, silica compounds, celluloses and caseins. It is made.

[(A) Aqueous resin] The aqueous resin is not particularly limited. However, considering the ease of handling of a coating agent, an aqueous dispersion resin is preferable to a water-soluble polymer. Specifically, acrylic emulsion, ionomer emulsion,
Acrylic / ionomer composite emulsions, polyolefin emulsions and the like are more preferred.

[Preparation of water-dispersed resin] The method for producing the water-dispersed resin used in the present invention is not particularly limited. Further, the aqueous dispersion resin used in the present invention,
Usually, it can be produced by a known mechanical emulsification method, emulsion polymerization method or the like. Examples of commercially available ionomer emulsions include Chemipearl S-100, S-650, and S-pearl.
659 (all are trade names manufactured by Mitsui Chemicals, Inc.). An example of polymerization of an acrylic emulsion by an emulsion polymerization method is described in JP-A No. 12-52502.

[(B) Additives] In the present invention, additives such as urea, polyethylene glycols (polyethylene glycol, polyethylene glycol monoester or diester), silica compounds such as colloidal silica, celluloses such as hydroxyethyl cellulose, Those having water retention and moisture retention such as caseins are exemplified. Of these, urea and polyethylene glycols are preferably used, and urea is more preferable. The amount of addition is not particularly limited, but the effect is small if the amount is small, and since the effect of improving the physical properties as much as added is not seen if the amount is too large, the amount is usually 0.3 to 100 parts by weight based on the solid content of the aqueous resin. 30 parts by weight are preferred. Further, these additives may be used alone, or two or more kinds may be mixed and used in an appropriate ratio.

[Other Additives] In addition, the following additives may be added, if necessary, as long as the heat sealability and other necessary physical properties are not impaired. Examples of the additives include waxes such as paraffin wax and carnauba wax, antistatic agents, ultraviolet absorbers, and antiblocking agents such as organic polymer fine particles and inorganic fine particles.

The heat-sealing multilayer structure of the present invention can be obtained by applying the heat-sealing coating agent thus obtained on a layer comprising a base material to form a heat-sealing layer.

[Substrate] The substrate is not particularly limited.
Polyolefin films and the like which can be generally used for packaging materials can be used. High-pressure low-density polyethylene, medium-low pressure high-density polyethylene, medium-density polyethylene, linear low-density polyethylene, polypropylene, polybutene-1, poly-
Unstretched film, uniaxially stretched film mainly composed of a polymer containing 50% or more of α-olefin such as 4-methylpentene-1, ethylene-vinyl acetate copolymer, ethylene-methacrylic acid copolymer, ionomer resin and the like; A biaxially stretched film is exemplified. Among them, a biaxially oriented polypropylene film, a biaxially oriented polyethylene terephthalate film, and a biaxially oriented polyamide film are preferable. The thickness of the substrate is not particularly limited, but is preferably 12 to 100 μm in consideration of the strength, processability, and economy of the film. Further, a surface treatment such as a corona discharge treatment may be performed to improve the adhesion between the heat seal layer and the substrate.

The above heat-sealable coating agent may be applied as it is on a substrate, or one or more primer layers may be provided between the substrate and the substrate. There is no particular limitation on the type of primer used.

The coating can be carried out by a known technique such as a gravure coater, reverse coater, kiss coater, air knife coater, Meyer bar coater, dip coater and the like. The coating can be applied to only one side or both sides of the film depending on the purpose. Furthermore, offline (coating after film forming),
Any method of in-line (application at the time of film formation) can be adopted.

The drying conditions are not particularly limited. Any temperature may be used as long as a transparent film is formed, and a hot air dryer or the like is usually used. The drying temperature is 60 to 180 ° C (depending on the coating method), and the drying time is about 2 seconds to 5 minutes. If necessary, a corona discharge treatment or the like may be performed after drying as a post-treatment.

The amount of coating is not particularly limited.
3g / m ² ~5.0g / m ² is preferred. If the thickness is too thin, a coating film defect or the like is generated, and sufficient heat sealing properties cannot be obtained. On the other hand, if the thickness is too large, it takes too much time and heat to heat seal, so that it is ineffective for cost.

[0017]

EXAMPLES Next, specific examples of resin composition, examples of application, and comparative examples will be described. However, the present invention is not limited by this embodiment. In addition,% which shows content is the weight% of solid content.
Is a part by weight.

Example 1 A coating agent was prepared by mixing Chemipearl S659 (manufactured by Mitsui Chemicals, Inc.) and urea (manufactured by Mitsui Chemicals, Inc.) in the amounts shown in Table 1. Perform corona discharge treatment on the polypropylene film vertically stretched by a biaxial stretching machine,
In the line, the coating agent is coated with a wire bar in front of the horizontal stretching zone, dried at 180 ° C. for 5 seconds, and stretched laterally as it is to form a heat-sealing multilayer having a coating amount of about 0.5 g / m ^2. A structure was obtained.

(Examples 2 and 3, Comparative Example 1)
The heat-sealing multilayer structure was obtained in the same manner as in Example 1 by blending as shown in Table 1 below to obtain a coating agent.

[0020]

[Table 1]

(Method of preparing test piece) Examples 1 to 3,
The heat-sealable structure obtained in Comparative Example 1 was cut into an appropriate size, and aged at 40 ° C. for about 20 hours to obtain a test piece.

Evaluation method (1) Heat sealing property Using a heat gradient sealer, a sealing temperature of 90 to 130 ° C. (1
Heat sealing was performed at a pressure of 1 kg / cm ² for 0.5 seconds at a temperature of 0 ° C.). The sample width was 30 mm, the 90 ° peel strength was measured at a pulling speed of 300 mm / min, and this was defined as the heat seal strength. If it is 1.0 N / 30 mm or more, it can be regarded as a practical level.

(2) Appearance The appearance of the coated test piece was visually judged. ○: transparent, ×: whitening

(3) Surface Specific Resistance Value (under Normal Humidity) A test piece is allowed to stand in a constant temperature / humidity room at 23 ° C. and 50% RH for a certain period of time, and a commercially available surface resistance measuring instrument, for example, Universal Electrometer Co., Ltd., Kawaguchi Electric Works, Ltd.
MMAII-17A Measured at an applied voltage of 100V.
If it is 10 ¹² Ω or less, it can be regarded as a practical level.

(4) Low Humidity Surface Specific Resistance The test piece is allowed to stand for a certain period of time in a constant temperature / humidity box at 30 ° C. and 30% RH together with a measuring instrument, for example, Advantest Digital Ultra High Resistance / Micro Ammeter R8340A. And applied voltage of 560V. As in (3), if it is 10 ¹² Ω or less, it can be regarded as a practical level.

(5) Blocking Resistance The coated surfaces of the test pieces cut into a square of 5 cm were overlapped with each other, and a load of 5 kg was applied thereto at 40 ° C. for 5 hours. After returning to room temperature, the state of the coating film after peeling when peeling the film, the manner of tearing of the base film, and the like were visually evaluated. ；: No peeling, Δ: peeling, ×: substrate tear

(6) Solvent resistance One drop of a solvent (toluene, ethanol, etc.) was dropped on the film, and the whitening state of the dried coating film was visually evaluated. ；: Transparent, △: partially whitened, ×: entirely whitened

(7) Water resistance The film cut into a 10 cm square was immersed in hot water of 90 ° C. for 30 seconds, taken out, and excess water was wiped off. The degree of whitening of the coating film was visually evaluated. ；: Transparent, Δ: partial whitening, ×: full whitening The evaluation results are shown in Table 2.

[0029]

[Table 2]

[0030]

According to the present invention, it is suitable for a packaging material having good workability even under low humidity, and is excellent in heat sealability, appearance, surface resistivity (high humidity, low humidity), solvent resistance and water resistance. And a low-temperature heat-sealable coating agent.

Continued on the front page F-term (reference) 4F006 AA12 AA13 AA35 AA38 AB24 BA13 CA07 4F100 AA20B AA20H AH02B AH02H AH03B AH03H AJ04B AJ04H AJ09B AJ09H JAKA JBBAJBBAJBBAJBBAJBBAJBBAJBBAJB BA192 CB001 CB051 CF031 CG141 DF022 HA446 JB23 MA08 MA10 NA03 NA04 NA12 NA27 PA18 PB02 PC08

Claims (5)

[Claims] 1. A low humidity surface resistivity (30 ° C., 30% R)
H, measured at an applied voltage of 560 V), which can form a coating film of 10 ¹² Ω or less. 2. A mixture comprising (a) an aqueous resin and (b) at least one additive selected from urea, polyethylene glycols, silica compounds, celluloses, and caseins. 2. The heat-sealing coating agent according to 1. 3. The heat-sealing coating agent according to claim 2, wherein the aqueous resin is a water-dispersed resin. 4. At least a part of (I) a layer composed of a base material and (II) a heat-sealing layer obtained from the heat-sealing coating agent according to any one of claims 1 to 3. A heat-sealing multilayer structure having two or more layers. 5. The heat-sealable multilayer structure according to claim 4, wherein the substrate is a polyolefin film.