LAMINATE

Abstract

The present invention provides a laminate having an adhesive layer excellent in low-temperature adhesiveness, water resistance, and hot water resistance. The laminate includes: a substrate; and an adhesive layer laminated on at least one surface of the substrate, in which the adhesive layer is obtained by drying a coated product of an aqueous dispersion containing water and a resin (X), and the resin (X) contains two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) each having a different content of a structural unit derived from an unsaturated carboxylic acid.

Claims

1. A laminate comprising: a substrate; and an adhesive layer laminated on at least one surface of the substrate, in which the adhesive layer is obtained by drying a coated product of an aqueous dispersion containing water and a resin (X), and the resin (X) contains two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) each having a different content of a structural unit derived from an unsaturated carboxylic acid.

2. The laminate according to claim 1, in which the total content of the structural units derived from an unsaturated carboxylic acid included in the two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) is 5 mass % or more and less than 18 mass % based on the total amount of structural units derived from monomers of the polymer contained in the resin (X).

3. The laminate according to claim 1, in which the two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) include one or more kinds of each of an ethylene-unsaturated carboxylic acid copolymer (a1) having a content of a structural unit derived from an unsaturated carboxylic acid of 12 mass % or more and 30 mass % or less, and an ethylene-unsaturated carboxylic acid copolymer (a2) having a content of a structural unit derived from an unsaturated carboxylic acid of more than 0 mass % and less than 12 mass %.

4. The laminate according to claim 3, in which the two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) satisfy at least one of the following conditions (i) and (ii): (i) including two or more kinds of ethylene-unsaturated carboxylic acid copolymers each having a different content of a structural unit derived from an unsaturated carboxylic acid as the ethylene-unsaturated carboxylic acid copolymer (a1); and (ii) including two or more kinds of ethylene-unsaturated carboxylic acid copolymers each having a different content of a structural unit derived from an unsaturated carboxylic acid as the ethylene-unsaturated carboxylic acid copolymer (a2).

5. The laminate according to claim 4, in which as the ethylene-unsaturated carboxylic acid copolymer (a1), an ethylene-unsaturated carboxylic acid copolymer (a1-1) having a content of a structural unit derived from an unsaturated carboxylic acid of 17 mass % or more and 30 mass % or less, and an ethylene-unsaturated carboxylic acid copolymer (a1-2) having a content of a structural unit derived from an unsaturated carboxylic acid of 12 mass % or more and less than 17 mass % are included.

6. A laminate comprising: a substrate; and an adhesive layer laminated on at least one surface of the substrate, in which the adhesive layer contains two or more kinds of ethylene-unsaturated carboxylic acid copolymers (a) each having a different content of a structural unit derived from an unsaturated carboxylic acid.

Description

EXAMPLES

[0126] Hereinafter, the present invention will be described in more detail on the basis of Examples; however, the present invention is not limited to these Examples.

Production Example 1

[0127] A resin obtained by melt-kneading 50 parts by mass of an ethylene-methacrylic acid copolymer (resin B) having a content of methacrylic acid of 15 mass % and 50 parts by mass of an ethylene-methacrylic acid copolymer (resin C) having a content of methacrylic acid of 10 mass %, 4.4 parts by mass of sodium hydroxide, and 190 parts by mass of deionized water were placed in a reaction vessel, stirred, heated to 150° C., held for 4 hours, and then cooled to room temperature to obtain an aqueous dispersion 1 of resin particles 1 of a resin 1. The average value of the contents (acid content average value) of the structural units derived from methacrylic acid in the resin 1 was 12.5 mass %, and the weight average particle diameter of the resin particles 1 was 0.5 μm. The viscosity of the aqueous dispersion 1 was 400 mPa.Math.s, the nonvolatile content (Nv) was 35%, and the melt flow rate (MFR) was 3.0 g/10 min.

Production Examples 2 and 3

[0128] Aqueous dispersions 2 and 3 were obtained in the same manner as in Production Example 1, except that, instead of the resin containing the resin B and the resin C of Production Example 1, a resin having a composition in Table 1 was used and a resin having a composition in Table 2 was used. Each physical property value is shown in Table 2.

Production Example 4

[0129] A mixture of 30 parts by mass of an ethylene-acrylic acid copolymer (resin A) having a content of acrylic acid of 20.5 mass % and 70 parts by mass of an ethylene-methacrylic acid copolymer (resin E) having a content of methacrylic acid of 4 mass % was supplied at a rate of 50 g/min from a hopper of a twin screw extruder (manufactured by Ikegai Ironworks Corp, PCM-30, L/D=40), a 3.5% aqueous solution of potassium hydroxide was continuously supplied at a rate of 28 g/min from a supply port provided in a vent portion of the extruder, the resin mixture was continuously extruded at a heating temperature of 110° C., and the extruded resin mixture was cooled to 90° C. with a jacketed static mixer installed in the extruder port and further introduced into hot water at 80° C. to obtain an aqueous dispersion 4. The weight average particle diameter of the resin particles 4 was 0.9 μm. The viscosity of the aqueous dispersion 4 was 300 mPa.Math.s, the nonvolatile content (Nv) was 37%, and the melt flow rate (MFR) was 1.0 g/10 min.

Production Examples 5 to 7 Production of Aqueous Dispersions 5 to 7

[0130] Aqueous dispersions 5 to 7 were obtained in the same manner as in Production Example 1, except that, instead of the resin containing the resin B and the resin C of

[0131] Production Example 1, a resin having a composition in Table 1 was used and a resin having a composition in Table 2 was used. Each physical property value is shown in Table 2.

TABLE-US-00001 TABLE 1 Resin A Resin B Resin C Resin D Resin E Resin 79.5 85 90 80 96  Methacrylic acid — 15 10 10 4 Acrylic acid 20.5 — — — — Isobutyl acrylate — — — 10 — MFR (g/10 min, 300   60 500  35 7 190° C.)

TABLE-US-00002 TABLE 2 Aqueous Aqueous Aqueous Aqueous dispersion 1 dispersion 2 dispersion 3 dispersion 4 Resin A — 40 40 30 Resin B 50 20 30 — Resin C 50 40 — — Resin D — — 30 — Resin E — — — 70 Acid content   12.5   15.2   15.7  9 average value Neutralizing NaOH(54%) KOH(30%) KOH(30%) KOH(30%) agent (neutralization rate) Production Autoclave Autoclave Autoclave Extrusion method phase inversion Charged Melt blend Melt blend Melt blend Single resin Nv (%) 35 42 42 37 Viscosity 400  200  300  300  (mPa .Math. s) Particle   0.5   0.5   0.5   0.9 diameter (μm) Aqueous Aqueous Aqueous dispersion 5 dispersion 6 dispersion 7 Resin A 100  — — Resin B — 100  — Resin C — — 100  Resin D — — — Resin E — — — Acid content   20.5 15 10 average value Neutralizing KOH(20%) NaOH(54%) NaOH(80%) agent (neutralization rate) Production Autoclave Autoclave Autoclave method Charged Single Single Single resin Nv (%) 42 27 33 Viscosity 200  500  900  (mPa .Math. s) Particle   0.3    0.02   3.8 diameter (μm) Nv: Nonvolatile content

Example 1

[0132] Base paper for a cup (basis weight: 170 g/m.sup.2) manufactured by Tami Nadu Newsprint and Papers Limited was used as a substrate, and the aqueous dispersion 1 was coated twice using an air knife coater so that the amount of resin coated was 6 g/m.sup.2, and dried at 130° C. for 20 seconds, thereby obtaining a paper coated article 1 as a laminate.

[0133] A soft aluminum foil (50 μm) was used as a substrate, and the aqueous dispersion 1 was coated once using a bar coater so that the amount of resin coated was 3 g/m.sup.2, and dried at 120° C. for 20 seconds, thereby obtaining an aluminum foil 1 as a laminate.

[0134] (Cobb Value)

[0135] The Cobb value of the paper coated article 1 was measured by the Cobb method (JIS P8140) for the amount of water absorption after 300 seconds (Cobb.sub.300), and evaluated according to the criteria described in Table 3. The results are shown in Table 4.

[0136] (Hot Water Resistance of Cup)

[0137] In a paper cup molded using the paper coated article 1, boiling water at 95° C. or higher was poured and left for 1 hour, and water leakage from the seal bonding portion was observed and evaluated according to the criteria described in Table 3. The results are shown in Table 4.

[0138] (Low-Temperature Adhesiveness)

[0139] The resin coated surfaces of the aluminum foil 1 were bonded to each other under the conditions of 110° C., 0.1 seconds, and 1 kg/cm.sup.2, and the peeling strength was measured under the condition of a tensile speed of 50 mm/min and evaluated according to the criteria in Table 3. The results are shown in Table 4.

[0140] (Blocking Resistance)

[0141] The aluminum foil 1 was cut into squares of 5 cm in length and width, the coated surfaces were superimposed on each other, and the blocking resistance under the conditions of 45° C., 250 g/cm.sup.2, and 24 hours was evaluated according to the criteria in Table 3. The results are shown in Table 4.

Examples 2 to 4

[0142] Paper coated articles 2 to 4 and aluminum foils 2 to 4 were obtained in the same manner as in Example 1, except that each of the aqueous dispersions 2 to 4 was used instead of the aqueous dispersion 1 in Example 1. Each physical property of Examples 2 to 4 was evaluated in the same manner as in Example 1, using the obtained paper coated articles and aluminum foils. The results are shown in Table 4.

Comparative Examples 1 to 3

[0143] Paper coated articles 5 to 7 and aluminum foils 5 to 7 were obtained in the same manner as in Example 1, except that each of the aqueous dispersions 5 to 7 was used instead of the aqueous dispersion 1 in Example 1. Each physical property of Comparative Examples 1 to 3 was evaluated in the same manner as in Example 1, using the obtained paper coated articles and aluminum foils. The results are shown in Table 4.

TABLE-US-00003 TABLE 3 S A B C Cobb Less than 5 g/m.sup.2 or 10 g/m.sup.2 or 15 g/m.sup.2 value 5 g/m.sup.2 more and less more and less or more than 10 than 15 g/m.sup.2 g/m.sup.2 Hot water — No water Water Water resistance leakage leakage leakage of cup partially occurs occurs Low- 500 g/15 Less than Less than Less than temperature mm or more 400 to 500 300 to 400 300 g/15 adhesiveness g/15 mm g/15 mm mm Blocking None Noise is Adhesion Adhesion resistance slightly partially entirely generated occurs occurs

TABLE-US-00004 TABLE 4 Comp. Comp. Comp. Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 1 Ex. 2 Ex. 3 Paper Cobb value S S S S S B C coated Hot water A A A A B A A article resistance of cup Blocking S A A S C S S resistance Aluminum Low-temperature A S S A S B C foil adhesiveness Blocking S A A S C S S resistance

[0144] [Measurement Method]

[0145] (Acid Content Average Value)

[0146] The acid content was measured by subjecting the resin to a base removal treatment, then melting the resin in tetrahydrofuran with heating, and titrating the resin with potassium hydroxide of a specified concentration in a heated state, and the acid content average value was calculated.

[0147] (Neutralization Rate)

[0148] The infrared absorption spectrum of the sample is measured, and a peak height “a” of absorption at 1700 cm.sup.−1 corresponding to the carboxy group is determined. The peak height “a” corresponds to the number of carboxy groups that are not ionically bonded in the resin.

[0149] The sample is brought into contact with hydrochloric acid to remove metal ions in the resin (demetallization), thereby obtaining an acid copolymer having no ionic bond (intramolecular crosslinking). The infrared absorption spectrum of the sample of this acid copolymer is measured, and a peak height “b” of absorption at 1700 cm.sup.−1 is determined. The peak height “b” corresponds to the number of all carboxy groups in the resin.

[0150] The neutralization rate (%) was calculated from the obtained peak heights “a” and “b” by the following formula.

Neutralization rate (%)=100(1−a/b)

[0151] (Viscosity)

[0152] The viscosity was measured at 25° C. using a B-type viscometer (manufactured by Toki Sangyo Co., Ltd.).

[0153] (Particle Diameter)

[0154] The average particle diameter of the resin particles was measured by Nanotrac Wave II (MicrotracBEL Corp.).

[0155] (Melt Flow Rate)

[0156] The melt flow rate (MFR) was measured according to ASTM D1238-65T under the conditions of 190° C. and a load of 2.16 kg.