CA1059889A

CA1059889A - Process for preparing laminated product

Info

Publication number: CA1059889A
Application number: CA229,127A
Authority: CA
Inventors: Yujiro Kosaka; Shinichi Imura; Tokio Fujiki; Hidenori Sako; Hideo Fujii
Original assignee: Toyo Soda Manufacturing Co Ltd
Current assignee: Tosoh Corp
Priority date: 1974-06-11
Filing date: 1975-06-11
Publication date: 1979-08-07
Also published as: AU475704B2; GB1456629A; HK23981A; AU8197875A; NL7504898A; JPS50156583A; JPS5316401B2

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides in a process for preparing a laminated product in which the lamination of sub-strates is effected with an adhesion-promoting agent the improvement in which the adhesion-promoting agent is an aqueous solution of an adhesion-promoting composition comprising 10 -300 wt. parts of starch or a modified starch and 100 wt. parts of polyethyleneimine.

Description

~s~g The present invention relates to a proce~s for preparinya laminated product using an adhesion promoting composition for extrusion lamination. ~;
Heretofore, the conventional adhesion-promoting comp-ositions for extrusion-coating and laminating have been organic solvent solution type compositions containing an organo-titanate or an isocyanate. These organic solvent solution type adhesion-promoting compositions have disadvantages of gelation caused by moisture; drainage treatment during gelation, the residual smell of solvent adsorbed in thelaminated layer; the discharge gas treatment of solvent generated in the coating step; and inflamm-ability, and their functions i.e. processibility or operability -~
as an adhesion-promoting composition are inferior.
Recently, oriented plastic films such as biaxial stretch-ed polypropylene film have been commercialized. These plastic films are swelled by the organic solvent type adhesion-promoting compositions. Accordingly, aqueous solution type adhesion-promo-; ting compositions such as polyethyleneimine type composition have been used. Adhesion-promoting composition containing polyethyleneimine as main components are of particular mention.
These compositions were disclosed in Japanese Patent Publication No. 9990/1961, Japanese Patent Publication No. 10490/1961, Japanese Patent Publication No. 32360/1970, U.S.P. No. 3,096,602, U.K. Patent No. 910,875, U.K. Patent No. 919,065, U.S.P. 3~4,09~, U.K. Patent No. 766,827, U.S.P. 3011910, U.S.P. 2,999,782, ~ G3 U.S.P. 2,828,237,and U.K. ~ . ~owever, the characteristics of these compositions as adhesion-promoting agents are not satis-factory. In particular conventional polyethyleneimine type adhesion-promoting compositions have disadvantages with respect to heat stability, hygroscopic properties, changes of adhesive strength on ageing, and adhesive strength per se.
The present invention provides a process for preparing 1- ~

, ."
.

~os~
a lamina-ted product which has hiyh adhesive strength and especi-ally a stable adhesive strength on ageing.
According to the present invention there is provided in a process for preparing a laminated product in which an adhesive-promoting agent is used to laminate the substrate, the improvement in which the adhesive-promoting agent is an aqueous solution desirably having a 0.01 - 5 wt.% solids concentration and including 10 - 300 wt. parts of starch or a modified starch and 100 wt. parts of polyethyleneimine; and if desirable 1 - 30 wt. parts of polyacrylic acid.
The aqueous solution used for extrusion-coating and laminating in the process of the present invention is referred to as an adhesion-promoting composition. It has been found that ~-a mixture of starch or a modified starch with polyethyleneimine ~ ~ `
is useful as a water soluble pressure-sensitive adhesive compo- ;
; sition because it has excellent characteristics with respect to hygroscopic properties coagulation resistance and heat stability ~`
as compared to those characteristics of conventional polyethylenei-~; mine type adhesive compositions.
The solidsconcentration of the adhesive composition is ~ ;
desirably not high. Thus, it has been found a dilute composition of the mixture is effective as an adhesion-promoting composition when it is applied for extrusion coating and laminating wherein high processability such as high speed coating and high adhesive strength are required. The dilute composition which contains said two or three components and has 0.01 - 5 wt.% solids concen-tration diluted with water or a mixture of water and water miscible medium e.g. alcohol, can be preferably used as an adhesion~promoting composition as it is satisfactory for imparting said characteristics. That is, various laminated products having high adhesive strength which is not substantially reduced in ageing; high heat resistance and heat stability in heat-sealing ~ 59~89 operations; and excellent non-hygroscopic properties which can be applied for various fields, can ~e prepared by coating said aqueous solution of adhesion-promoting agent on a surface of cellulose film, aluminum foil, polypropylene film and the like, and then drying it and coating or laminating thermoplastic i polyolefin such as polyethylene and polypropylene.
` In the process of the present invention, the water ; soluble adhesion-promoting composition comprising polyethylene-imine and starch or a modified starch and if desired polyacrylic acid is coated on a surface of a substrate such as cellulose ;
film, aluminum foil or polypropylene film and a thermoplastic ~
polyolefin such as polyethylene is coated or laminated on the -surface, to prepare various types of laminated prodcuts.
The polyethyleneimine is suitably prepared by polymeriza-tion of ethyleneimine, and preferably has a viscosity of 300 -10,000 cps preferably 400 - 5,000 cps, (as 30~ aqueous solution measured by Brookfield viscometer at 25C) and pH of 8 - 11 -(as 5~ aqueous solution).
The starch used in the process of the present invention is preferably a soluble starch. It is preferable to use water soluble modified starches. These modified starches are disclosed in Encyclopedia of Polymer Science and Technology Vol. 12, pages 833 - 844. The modified starch can be aninorganic acid starch `~
ester such as a sulfate or phosphate or an organicacid ester ~ ;
such as an acetate, an organic sulfonate; or salts thereof, ether derivatives and cationic derivatives. It is preferable that the modified starch is a phosphated starch or phosphated starch -modified with urea, acid amides or other nitrogenous material.
The phosphated starch preferably has a degree of substitution of 0.001 - 3.0, more preferably 0.01 - 1.5 (substituent per one anhydro-glucose unit). The other modified group of the modified starch is in same range. The amount of the starch or the modified starch in the composition is lO - 300 wt. parts preferably 15 -200 wt. parts per 100 wt. parts of polyethyleneimine.
; The polyacrylic acid used for the three component type water-soluble adhesion-promoting composition for use in the ` process of the present invention preferably has a viscosity of l,000 - 20,000 cps and more preferably 5,000 - 15lO00 cps (as 25 % aqueous solution measured by srookfield viscometer at 30C) and pH of 1.0 - 3.0 (as 1% aqueous solution at 25 C). The ratio of starch or a modified starch and polyacrylic acid to -` lO polyethyleneimine is usually 10 - 300 wt. parts of starch or a ;~ modified starch and l - 30 wt. parts of polyacrylic acid per ~
lO0 wt. parts of polyethyleneimine and preferably 15 - 200 wt. ~, parts of starch or a modified starch and 3 - 25 wt. parts of ; polyacrylic acid per lO0 wt. parts of polyethyleneimine.
` The two component or three component adhesion-promoting composition in the process of the present invention is coated .~
` on the surface of various type substrates by such methods as the ;~ roller-coating method and the dropwise coating method. When the solids concentration of the adhesion-promoting composition ~ ;
".''!, 20 i5 higher than 5 wt.%, the wetability, processability and drying ~, properties of the adhesion-promoting composition are inferior `~ to decrease the productivity of the laminated product. According-~^~ ly, the two component or three component adhesion-promoting composition is desirably applied at a solids concentration of 0.01 - 5 wt.% and more preferably 0.1 - l wt.% ;
; It is preferable to add a small amount of alcohol or ,~ ketone to the composition to increase its drying speed and to prevent shrinkage of the substrate. The alcohols and ketones ~
... ,, :
- are preferably water-soluble having a boiling point lower than that of water, and include methanol, ethanol, isopropanol, acetone and mixtures thereof. The ratio of the alcohol or ketone , ~ :
,, .
.
.
:~ : , , - . , . :

to water in the composition is 10 : 90 ~ ~0 : 20 by we-ight prefer-ably 10 : 90 ~ 60 : ~0 by weight.
The adhesion-promoting composition of the present -invention haviny a suitable concentration, may be prepared by directly mixing the components or to dilute a concentrated solution of the components to said suitable concentration. When a concentrated solution is diluted to suitable concentration, an emulsification somtimes takes place. The emulsified composi-tion can be applied. However the emulsification can be prevented by adding 1 ~ 30 wto parts of an acidic component such as acetic , acid, hydrochloric acid or tartaric acid or a basic component such as a sodium carbonate to the components in the aqueous solu-tion of the two component or three component adhesion-promoting ; composition, without reducing its advantagous properties.
The substrates which can be used for the lamination ~ -process of the present invention using the two component or three component adhesion-promoting composition include cellulose film, non~swellable cellulose film, monoaxial stretched polypropylene film, biaxial stretched polypropylene film, polyester film, aluminum foil, non-woven fabric, paper, synthetic paper, low density polyethylene film, high density polyethylene film and ..
polyvinylidene-vinyl chlroide-coated nylon which are printed or unprinted. The resin for extrusion-coating or laminating can be thermoplastic polyolefins such as low denisty polyethylene, high density polyethylene, and polypropylene.
The present invention will be further illustrated by way of the following Examples.
Examples 1 - 3 A plurality of aqueous solutions were prepared each having a 10 wt. % solids concentration by admixing the following components and each solution was diluted with a mixture of 50 wt. % of water and 50 wt. % of methanol to form a dilute solution .

~98~5~

havin~ a 1 wt. % solids concentration.

Phosphated starch modified with urea containing 6.0% of nitrogen (and 1.2~ of phosphorus Polyethyleneimine ~670 cps of viscoosity oE 30~ aqueous~
solution at 25 C;
; pH of 10 of 5~ aqueous solution Polyacrylic acid ~8,300 cps of viscosity at 30C;
~pH ofo2.2 of 1% aque J

Acetic acid (pure) Each dilute solution was coated on a surface of cell- -~

;~ ulose film (PT 300 Japanese Industrial Standard Z 1526 manufact- -.
ured by Tokyo Cellophane K.K.) by a roller coater at a processing speed of 70 m/min., so as to give a rate of 1 - 2 g/m2 wet.
The coated cellulose film was dried at about 90C by . passing it through a drier tunnel. A molten polyethylene (melt index of 8 g/10 min. density of 0.917 g/cc) extruded at the temperature of 315C was coated on the under-coated cellulose film in thickness of 20 ~, and then monoaxial stre-tched poly-propylene film (manufactured by Futamura Kagaku K.K.) was laminated on the coated surface. These steps were carried out on in line system. The peel strength hetween the cellulose film and the polyethylene of the three layer laminated film was measured. The results are shown in Table 1 together with the ~ ~
formula of the adhesion-promoting composition. ;

..
.

.

; ' ' .,: ' ::
Table 1 ~
, ,, Example Formula of adhesion-promoting Peel composition strength -(g/15 mm width) - 1polyethyleneimine 7 wt.parts amino-phosphated -~
starch 3 " 755 water go "
, ~ . _ ~ -2polyethyleneimine 7 wt.parts amino-phosphated starch 2.5 l 830 polyacrylic acid 0.5 " ~-~
water 90 , ,~ . . .. _ ._ _ __ ; 3polyethyleneimine 7 wt. parts ;
amino-phosphated ;~
starch 2.5 1l polyacrylic acid 0,5 ~l 800 acetic acid 0.5 1l ~ .
_ water 89.5 " ;

:7 ~ .
;( 20 The peel strength was measured under the following conditions. -Tensile tester Schopper's tensile tester(manufactured by Toyo Seiki K.K.) , peeling speed 150 mm/min.
7 Distance between chucks 100 mm Width of test sample 15 mm Reference 1 s In accordance with the process of Example 1l except ;
using 5.8% polyethyleneimine solution (10% of water; 90% methanol) as an adhesion-promoting agent, a three layer laminated film was prepared, and the peel strength of the laminated film was only 495 g/15 mm width. ; -~,. .
' , ' ' ' E mple 4 An aqueous solution havlng 10 wt.% of solid concentxa-tion was prepared by admixing the Eollowing components and the solution was diluted with a mixture of 60 wt.% of water and ~0 ~ -wt.% of methanol to form a plurality of dilute solutions each having a 1, 2 or 3 wt.% solids concen-tration.
Polyethyleneimine 7 wt. parts Amino-phosphated starch 2.5 "
Polyacrylate 0.5 "
Water 90 "
(The components are same with those in Examples 1 - 3).
In accordance with the process of Example 1, each dilute solution was coated on a biaxial stretched polypropylene film and then molten polyethylene (melt index of 8 g/10 min.; density of 0.917 g/cc) was coated on the under-coat surface at a thickness of 20 ~.
The heat resistance of the laminated film was measured by a heat sealer. The laminated film was heat-sealed at 120 -280C under the pressure of lKg/cm2G for 1 second, and the color change of the heat-sealed part was tested. Although the shrinkage of the biaxial stretched polypropylene film was found but no yellowish color change was found. The color change was further tested by heat-sealing the laminated film at 150C, under the pressure of 1 Kg/cm2G for ~ seconds, no color change was found.
The thermal stability of the laminated film is a remarkable advantage when the adhesion-promoting composition is applied for a transparent substrate.
Reference 2 In accordance with the process of Example 4, except using the adhesion-promoting agent of polyethyleneimine of Reference 1, the color change was tested. In the conditions of Example 4, the laminated film was changed to yellowish color.

~L~59~1~9 ~:
Example 5 An a~ueous solution having lO wt.9o of solid concentra-tion was prepared by admixing the followiny components and the solution was diluted with a mixture of 60 wt.~ of water and 40 wt.~ of methanol to form a dilute solution having l wt.~ of solids concentration.
Polyethyleneimine 7 wt. parts Amino-phosphated starch 2.5 "
Polyacrylic acid 0.5 "
Water 90 "
(The components are same with those of Examples l - 3) The dilute solution was coated on a surface of the cellulose film (PT 300) of Example l or the biaxial stretched polypropylene film of Example 4, by a roller coater at processing ~ ' , speed of 70 m/min., so as to give a rate of 1 - 2 g/m2 wet.
Each coated film was dried at about 90 C by passing through a drier tunnel. A molten polyethylene (melt index of 8 : , ~ g/10 min.; density of 0.917 g/cc) extruded at the temperature ', - of 315C was coated on each film at a thickness of 20 ~
The peel strength be-tween the cellulose film and polyethylene (or between the biaxia'l stretched polypropylene ~ `
film and polyethylene) of the lamina-ted film on ageing was tested.
It was found that the peel strength was not changed on ageing, as shown in Table 2.
'Table'2 -:
.. ,.. ... __ .
Substrate 5 days 30 days (g/15 mm width) (g/15 mm width) ,,, , ,,. .... ... .. .. . ....... ..... . . ... ..
........ _.. _ Cellulose film polyethylene polyethylene layer layer (PT 300) broken broken ,,,,,,, _ 315 325 Biaxial stretched polyethylene polyethylene ' polypropylene layer layer (25~ thickenss) broken broken _ _, _ g _ ~59~9 Example 6 An aqueous solution having 10 wt.% of solids concentra-tion was prepared by admixing the following components and the solution was diluted with a mixture of 60 wt.% of water and 40 wt.
% of methanol to form a dilute solution having 1 wt.~ of solids concentration.
Polyethyleneimine 7 wt. parts Amino-phosphated starch 2.5 "
Polyacrylic acid 0.5 "
Water 90 (The components are same with those of Examples 1 - 3) The dilute solution was coated on each surface of a cellulose film (PT 300 of Japanese Industrial Standard); a biaxial stretched polypropylene film (25 ~ of thickness); aluminium I ~ foil (15 ~ of thickness); nylon~ film (15 ~ of thickness);
; polyester film (15 ~ of thickness) or a nonswellable cellulose film (MST 300 of Japanese Industrial Standard) by a roller coater at a processing speed of 70 m/min. so as to give a rate of 1 - 2 g/m2 wet. The coated film was dried at about 90C by passing

2 through a drier tunnel.
A molten polyethylene (melt index of 8.0 g/10 min.;
density of 0.917 g/cc) extruded at the temperature of 31~C was coated on each under coated film in thickness of 20 ~. The adhesive strength between each film and polyethylene of the two layer laminated film was measured. The results are shown in Table 3 wherein excellent results are set forth.

~ .

~59~313'g Table 3 , _ , Film Peel strength (y/15 mm width) .... _ _ Cellulose film polyethylene layer broken PT 300 of JIS Z1256 300 manufactured by Tokyo Cellophane : -Biaxial stretched polypropylene film polyethylene layer broken 25 ~ of thickness ~P 2102 manufactured by Toyobo K.K. 320 Aluminum foil polyethylene layer broken 15 ~ of thickness; metallic ~n one surface manufactured by 300 Tokai K;inzoku K.K.

Polyester film Unpeelable because of high 15 ~ of thickness; diafoil # 12 adhesive strength manufactured by Mitsubishi ~' Jushi K.K.
Nylon~ film 15 ,u of thickness 200 ~:
manufactured by Kojin K.K.

:. . _, , Nonswellable cellulose film MST 300 of JIS Z 1526 150 Manufactured by Tokyo Cel1ophane ', ,~ . -Example 7 An aqueous solution ha~ing 10 wt.% of solids concentra~

tion was prepared by admixing the followingc~mponentsand thesolu-tion was diluted with a mixture of 50 wt.% of water and 50 wt.%
of methanol to form a dilute solution having 1 wt.% of solids concentration.
Polyethyleneimine 7 wt. parts Soluble starch 2.5 "

:
91~
`, :
Polyacryllc acid 0 . 5 wto parts ~`~ Water 90 "
The dilute solution was applied in accordance with Example 1. The peel strength was 760 (g/15 mm width).

'.j 1 0 , ::~
;~. :
. ~ :

.
~'. ~"''.

~'f ''~ '.',~
'j ' "'.

' .'' '' :,~

~, ~
"`' :, .
,,- :
:",:

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. In a process for preparing a laminated product in which the lamination of substrates is effected with an adhesion promoting agent the improvement in which the adhesion-promoting agent is an aqueous solution of an adhesion-promoting composition comprising 10 - 300 wt. parts of starch or a modifed starch and 100 wt. parts of polyethyleneimine.

2. A process according to Claim 1, wherein the adhesion-promoting composition comprises 10 - 300 wt. parts of starch or a modified starch and 1 - 30 wt. parts of polyacrylic acid and 100 wt. parts of polyethyleneimine.

3. A process according to Claim 1, wherein the aqueous solution of the adhesion-promoting composition having a solids content of 0.01 to 5 wt.% is coated on the surface of a substrate and after drying the coating a thermoplastic polyol-efin is laminated thereon.

4. A process according to Claim 1, wherein the adhesion-promoting composition comprises 10 - 300 wt. parts of a phosphated starch or a phosphated starch modified with urea, acid amides or nitrogenous material and 100 wt. parts of poly-ethyleneimine.

5. A process according to Claim 4, wherein the adhesion-promoting composition comprises 10 - 300 wt. parts of a phosphated starch or a phosphated starch modified with urea, acid amide or nitrogenous material, 1 - 3 wt. parts of poly-acrylic acid and 100 wt. parts of polyethyleneimine.

6. A process according to Claim 1, wherein 1 - 30 wt.
parts of an acidic or alkaline component present to the aqueous solution to reduce emulsification.

7. A process according to Claim 1, wherein the aqueous solution contains an alcohol or ketone at a rate of 10 - 80% to 90 - 20% of water.

8. A process as claimed in claim 4 in which 15 to 200 wt. parts of the starch or modified starch are present.

9. A process as claimed in claim 5 in which 15 to 200 wt. parts of the starch or modified starch and 3 to 25 wt.
parts of polyacrylic acid are present.

10. A process as claimed in claim 3 in which the solution has a solids content of 0.1 to 1 wt.%.

11. A process as claimed in claim 3 in which the thermoplastic resin is extrusion laminated.