CA2068386A1

CA2068386A1 - Water soluble multilayer film for packaging alkaline materials

Info

Publication number: CA2068386A1
Application number: CA002068386A
Authority: CA
Inventors: Amir Famili; Finn Lennart Marten; James Francis Nangeroni
Original assignee: Individual
Current assignee: Air Products and Chemicals Inc
Priority date: 1991-05-17
Filing date: 1992-05-11
Publication date: 1992-11-18
Also published as: EP0513692A1; JPH06320683A; AU1619992A; AU649534B2; US5362532A

Abstract

ABSTRACT

A multilayer structure, especially a multilayer film, for packaging alkaline, or caustic, compositions. The multilayer structure consists essentially of:
(1) a first layer of an acid functional polymer that is soluble in aqueous alkaline medium, (2) a second layer of a partially hydrolyzed, thermoplastic PVOH, and, optionally, (3) a third layer of a fully hydrolyzed, thermoplastic PVOH.

Description

2~838~

PATENT - 184PUS04~83 WATER SOLUBLE MULTILAYER FILM FOR PACKAGING
ALKALINE MATERIALS

TECHNICAL FIELD
The present invention relates to multilayer polymeric structures, particularly multilayer polymeric films containing a polyvinyl alcohol (PVOH) layer.

BACKGROUND OF THE INVENTIO~
Many common chemicals that are used by dispersing or dissolvlng in water are inittally produced and packaged in powdered form. Examples of water dispersed or dissolved chemicals are agricultural chemicals such as pesticides which are applied as a water spray, caustic cleaners and 10 detergents, and process chemicals such as pigments, dyes and carbon black.
There are, however, several problems associated with the use of these products due to their to~icity or high concentratlon. Such problems include accidental exposure of the user or the immed~ate environment to the chemicals, accuracy in measurement during the addition of the chemical to 15 water tanks, and, finally, the disposal of the package in which the chemicals were delivered.
For the above reasons there has been a keen interest in packaging water soluble or water dispersible chemicals in water soluble films. Such packages would have the following advantages: human contact with the 20 concentrated chemical would be eliminated, accurate dosages of the chem~cals would be assured, and the disposal problem would be eliminated~
~ hile there are water soluble PVOH films available for packaging materials, such PVOH films typically lack the alkaline stability necessary for packaging alkaline, or caustic, compositions such as cleaning products 25 and detergents. ~ypically, a partially hydrolyzed PVOH is used to produce the cold water soluble film for packaging the alkaline product. However, the partially hydrolyzed PVOH being in contact with the alkaline product will undergo further hydrolysis reaction to produce a fully hydrolyzed PVOH
film.

8 ~

This fully hydrolyzed film has two major drawbacks. First, due to an increase in the overall degree of hydrolysis of the PVOH, the film becomes cold water insoluble. Secondly, a fully hydrolyzed PVOH film is highly crystalline. This highly crystalline film is more brittle and subject to cracking at low humidity which may result in accidental spillage of the chemicals and contamination of both humans and the environment.
Many attempts have been reported to improve the pH stability of the PVOH films. These efforts have ~ncluded the select~on of a special plast~c~zer: U.S. 2,948,697; 3,106,543 and 3,157,611; or blend~ng P W~l with an alkaline, stable water soluble polymer such as d~sclosed ~n U.S.
2,850,741; 3,695,989; 3,392,905; 4,481,326 and 4,692,494. Other approaches to producing a pH stable PVOH have been-dlrected at the modification or copolymer~zat~on of polyvinyl alcohol as d~sclosed in U.S. 3,441,547;

3,S05,303; 4,747,976 and 4,844,828.
U.S. 4,692,494 discloses water soluble films of polyvinyl alcohol and polyacrylic acid and packages comprising same.
In addition to PVOH films, there are alkaline water soluble, acid functional resins which include copolymers of ~meth)acrylates and (meth)acryl~c acid offered by Belland AG under the trademark BELLAND 2620 20 and 2585. However, these films either lack tensile strength or are very brittle and crack at low temperatures and relative humldity.
EP O 415 357 A discloses a method for producing thermoplastic PVOH
compositions.

SUMMARY OF THE INVENTION
The present invention provides a multilayer structure, especially a multilayer film, for packaging alkaline, or caustic, compositions. The multilayer structure consists essentially of:
(1) a first layer of an acid functional polymer that is soluble in aqueous alkaline medium, (2) a second layer of a partially hydrolyzed, thermoplastic PVOH, and, optionally, (3) a third layer of a fully hydrolyzed, thermoplastic PVOH.
The first layer is in contact with the alkaline composition of the package.

2~3~6 The multilayer structure thus provides a cold water soluble package when it comprises two layers, the outer layer being the partially hydrolyzed PVOH, and a hot water soluble package when it comprises three layers, the outer layer being the fully hydrolyzed PVOH. The structure may be any 5 article that is suitable for at least partially enclosing the caustic materials such as containers, pouches, envelopes, bottles and the like.
Moreover, the water soluble layers as films are transparent, non-tacky, heat sealable, thermoformable and mechan~cally strong. The multilayer structure is stable during storage over a wide range of temperatures and humid'ty. Since the alkaline contents of the package is in contact wlth the first layer and not the partially hydrolyzed PVOH, an alkaline stable, self-supporting packaging structure is obtained.

DETAILED DESCRIPTION OF THE INVENTION
The invention provides a water soluble, multilayer film especially suited for packaging pulverulent, powdery or solid caustic chemicals which are to be dissolved or dispersed in an aqueous med~um in their application.
The film consists essentially of:
(1) a first, or inner, layer of a water insoluble acid funct~onal polymer which is, however, soluble in a basic, aqueous medlum;
(2) a second layer of a cold water soluble, partially hydrolyzed, thermoplastic PVOH, and, optionally, (3) a third, or outer, layer of warm water soluble, fully hydrolyzed thermoplastic PVOH.
25 The thickness of each layer could vary between 0.5 to 5 mils depending upon the end use application. The sur~aces of the individual layers are heat sealable to each other, for example, along their common edges or over all or part of their adjacent surfaces.
The inner layer which is insolllble in neutral aqueous media, but soluble in a basic aqueous medium, comprises an acid functional polymer.
Acid functional means the polymer contains pendant carboxylic ~-C02H) or sulfonic (-SO3H) acid groups. Polymers that may be suitably used include those copolymers or terpolymers of Cl-C8 alkyl (meth)acrylates and (meth)acrylic acid from Belland AG under the trademark BELLAND 2620 and 2585 2~3~6 such as, for example, butyl methacrylate/ethyl acrylate/methacryl~c acid terpolymers. U.S. 4,612,355 teaches a method for making such alkyl (meth)acrylate/- (meth)acrylic acid copolymers which ls incorporated by reference. The Belland resins can be processed on typical plastic processing equ~pment such as a polyethylene screw with a 2.5:1 compression rat~o, square p~tch and 24 (61 cm) diameter long. Start-up conditlons on the barrel are typically 130-155C while maintaining the melt below 160C.
Also suitable as the resin for the f~rst layer are ethylene-acrylic acid copolymers, for example having 20% acrylic acid, sold under the trademark Primacor by Dow Chemical Co. or styrene-maleic anhydride copolymers available from Monsanto Co. and Arco Chemical Co. The purpose of this first layer is to protect the seco~d, or partially hydrolyzed PVOH, layer from direct contact with the alkal~ne contents ln order to maintain the cold water solubility and flexibil3ty of the partially hydrolyzed PVOH
layer. The problem of hydrolysis to fully hydrolyzed PVO~ is avoided. Thls first layer also provides a film whose performance is not affected over a wide range of temperature and humidity.
The second layer consists essentially of a partially hydrolyzed thermo-plast~c PVOH film. Suitable PVOH s for th~s second layer are those wh~ch are ~5 to 90 moleX, preferably 86-89 mole%, hydrolyzed and have a degree of polymeri~ation (DPn) in the range of 200 to 2,~00, i.e., viscos~ttes of 2 to 30 cps at 20~C as 4% aqueous solutions. Also su~table are vinyl alcohol copolymers which contain methyl methacrylate as disclosed ln U.S. 3,689,469 or copolymers containing up to 3-4 mole70 other copolymerized monomer.
The second, or partially hydrolyzed PVOH, layer acts as a support film for the inner layer, thus eliminating the cracking of the acid functional polymer layer. It also provides structural integrity and flexibility to the package and provides for cold water solubility.
0ptionally, but preferably, a third layer of a cold water insoluble (warm water soluble~ PVO~I film can be incorporated into the structure to reduce the tackiness of the film and premature disintegration of the package during handling in a wet environment, e.g., handling the package with a wet hand. This third layer also minimizes the effect of high humidity on the film structure. But most importantly, this third layer provides a warm 2~ 3~6 water soluble film which would lead to the disintegration of the packaging only in an application that utilizes warm or hot water not cold water.
~arm water is intended to mean water that is at least 60C.
The suitable resin composition for this third layer is a PVOH which is 95-99+ moleZ hydrolyzed preferably 98-99 mole% hydrolyzed and possesses a degree of polymerization in the range of 200 to 2 500.
Since the preferred method of produc~ng the multilayer structure is by direct co-extrusion of the resins using cast or blown film processes well known in the art of melt extrud~ng resins the PVOH resins used for the second and third layers must be melt extrudable thermoplastic compositions. U.S. Patent Application Serial No. 07t402 167 filed 1 September 1989 discloses a method for-producing such melt extrudable PVOH
compositions wh~ch appl~cation ~s incorporated by reference. Suitable melt extrudable PVOH compositions are marketed by Air Products and Chemicals Inc. under the trademark VINEX and can be used directly in the co-extruder.
Vinex PVOH resins can be processed on typlcal plast~c processing equ~pment such as a polyethylene screw with a 2.5:1 compression ratio square pltch and 24 (61 cm) diameter long. Start-up condit~ons on the barrel are typically 195-220C while maintaining the melt below 225C.
Alternatively the thermoplastlc PVOH composition can be generated inside the co-extruder itself by using a commerc~al grade PVOH and follow~ng the teachings of the 402 167 patent appl~cat~on. To generate the melt extrudable PVOH compositions in sttu a suitable plast~cizer would be blended with the appropr~ate PVOH. Such plast~c~zer would be compatible 25 with the PVOH and may be a polyhydr~c alcohol most preferably glycerol polyethylene glycol or other hydrophil~c compounds known in the art to possess compatibility with PVOH. Suitable hydrophilic plasticizers include ethylene glycol diethylene glycol trimethyol propane~ mannitol pentaerythritol or other polyhydric low molecular weight alcohols block of polymers of ethylene oxide and propylene oxide non-hydroxylic plasticizers such as aromatic amides and aromatic sulfonamides and are added to the composition in amounts ranging from 1-30 wt% preferably 3-20 wt% based on PVOH.

2~386 The thermal stab~l~ty of the PVOH can be further improved through the addition of a small amount of a m~neral acid preferably phosphoric acid to the PV~H and plast~c~zer blend prior to extruslon or by removing the resldual ash (sodlum acetate measured as Na20) through washing with an appropriate solvent. Optionally but advantageously a dispersing agent such as glycerol mono-oleate (GMO) is added during the blending operation to reduce lumping.
The multtlayer structure can be constructed elther by extruding a single layer film of each polymer composit~on and then heat laminating the films together using equipment well known in the art for this purpose or by co-extruding the thermoplast~c PVOH resins together using a blown or cast extrusion process and then heat laminat~ng the acid functional resin to the partially hydrolyzed PVOH layer. The most preferred way of producing the multtlayer structure is by direct co-extrusion of the three resins using a cast ~r blown film process and heat lamination (the hot extruded films being pressed together).
A multllayer film of thls lnventlon is water soluble transparent tough flexlble caustlc reslstant heat sealable thermoformable and stable durlng storage over a wide range of temperature. The thlckness of each layer could vary between O.S to S m~ls preferably between 1 to 3 mlls dependlng upon the end use appllcatlon.
Three layered pouches are not tacky to the wet hand and can be dissolved completely ~n warm alkallne water. However if a cold watersoluble caustlc resistant film is requ~red for packaging chemicals such as laundry detergent in which rapid dispensing of the detergent is required at the beginning of the wash cycle the two-layered pouch comprising the acid functional polymer inner layer and the partially hydrolyzed thermoplastic PVOH outer layer is more suitable.
:

Vinex 2034 resin a 87-89 mole% hydrolyzed thermoplastic PVOH having a DPn of 650 was extrus~on cast ~nto a f~lm under the follow~ng conditions ~n a 1 inch (2.54 cm) diameter 24:1 L/D Killion single screw extruder with a 3:1 compression ratio screw and an 8 inch (20.3 cm) coathanger die:

' 3 `3 ~

Zone 1: 200C
Zone 2: 200C
Zone 3: 200C
Die: 200C
Screw Speed: 52 rpm Die Press. 2590 psig (36,800 kg/cm2) Motor Load: 13.5 amps The film was smooth, clear, and free of gels. The V~nex 2034 film at 1.5 mil thlckness was then heat laminated at 130-140C to Belland 2620 polymer film (1.5 mils).

EXAMPL~ 2 V~nex 1003 resin, a 98-99 mole% hydrolyzed thermoplastic PVOH havlng a DPn of 750, was extrusion blown into a film in a 1 inch (2.54 cm) Killlon single screw extruder. The extruder was 24:1 L/D with a 3:1 compress~on ratio screw. The extrusion conditions were as follows:
Zone 1: 225C
Zone 2: 220C
Zone 3: 215C
Adaptor: 210C
Die: 220C
Screw Speed: 40 rpm ,.
Die Press. 1010 psig (14,400 kgJcm2) Motor Load: 14 amps The film was smooth, with a slight haze indicative of crystallization and therefore, cold water resistant and free of gels. The Vinex 1003 film at 1.5 mil thickness was then heat laminated to Vinex 2034 film (1.5 mils) and Belland 2620 film (1.5 mils) in such an order as to provide ~elland resin as the inner layer, Vinex 2034 resin as the middle layer and Vinex 1003 resin as the outside layer.

Film samples of the multilayer structures of Examples 1 and 2 were converted to pouches using an impulse heat sealer. The pouches were then 3 3 ~

filled with concentrated laundry detergent and evaluated for caustic stability and water solubil~ty by storing at 50% R.H. and 75F ~24C) for a period of 14 days. After the 14 days of storage the pouches appeared unchanged. The pouches were then placed with slow agitation in 500 ml water at the temperature indicated in Table 1. The times required for opening and total solubility of the film are presented in Table 1 showing seconds for the pouch to open and minutes for it to dissolve.

Sec. to Open Min. To Dissolve Sec. to Open Mln. to Dissolve Film 120F 120F S0F 50F
Ex 1 - - - 30 3 Ex 2 35 4 lS Vinex 2034 - - 180 large pieces undissolved The present invention provides a multllayer water soluble structure that ls suitable for packaging caust~c compositions such as laundry ~o detergents.

Claims

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

1. A multilayer structure comprising a first layer of an acid functional polymer and a second layer of a partially hydrolyzed, thermoplastic polyvinyl alcohol.

2. The multilayer of Claim 1 in which the acid functional polymer is selected from the group consisting of copolymers of alkyl (meth)acrylate and (meth)acrylic acid, copolymers of ethylene and acrylic acid, and copolymers of styrene and maleic anhydride.

3. The multilayer of Claim 1 in which the acid funtional polymer is a copolymer of alkyl (meth)acrylates and methacrylic acid.

4. The multilayer of Claim 1 in which the partially hydrolyzed polyvinyl alcohol is 75 to 90 mole% hydrolyzed and has a degree of polymerization in the range of 200 to 2500.

5. The multilayer structure of Claim 1 further comprising a third layer of a fully hydrolyzed, thermoplastic polyvinyl alcohol.

6. The multilayer of Claim 5 in which the fully hydrolyzed polyvinyl alcohol is 95 to 99+ mole% hydrolyzed and has a degree of polymerization in the range of 200 to 2500.

7. A multilayer structure comprising a first layer of an acid functional polymer selected from the group consisting of copolymers of alkyl (meth)acrylate and (meth)acrylic acid, copolymers of ethylene and acrylic acid, and copolymers of styrene and maleic anhydride and a second layer of a thermoplastic polyvinyl alcohol which is 75 to 90 mole% hydrolyzed and has a degree of polymerization in the range of 200 to 2500.

8. The multilayer structure of Claim 7 in which the polyvinyl alcohol is 86 to 89 mole% hydrolyzed.

9. The multilayer structure of Claim 7 further comprising a third layer of a thermoplastic polyvinyl alcohol which is 95 to 99+ mole%
hydrolyzed and has a degree of polymerization in the range of 200 to 2500.

10. The multilayer structure of Claim 9 in which the polyvinyl alcohol of the third layer is 98 to 99+ mole% hydrolyzed.

11. A multilayer structure comprising a first layer of an acid functional polymer selected from the group consisting of copolymers of alkyl (meth)acrylate and (meth)acrylic acid, copolymers of ethylene and acrylic acid, and copolymers of styrene and maleic anhydride, a second layer of a thermoplastic polyvinyl alcohol which is 86 to 89 mole% hydrolyzed and has a degree of polymerization in the range of 200 to 2500, and a third layer of a thermoplastic polyvinyl alcohol which is 98 to 99+ mole% hydrolyzed and has a degree of polymerization in the range of 200 to 2500.

12. The multilayer structure of Claim 1 which is a film.

13. The multilayer structure of Claim 2 which is a film.

14. The multilayer structure of Claim 3 which is a film.

15. The multilayer structure of Claim 4 which is a film.

16. The multilayer structure of Claim 5 which is a film.

17. The multilayer structure of Claim 6 which is a film.

18. The multilayer structure of Claim 7 which is a film.

19. The multilayer structure of Claim 8 which is a film.

20. The multilayer structure of Claim 9 which is a film.

21. The multilayer structure of Claim 10 which is a film.

22. The multilayer structure of Claim 11 which is a film.

23. A package containing alkaline material and formed from the film of Claim 12.

24. A package containing alkaline material and formed from the film of Claim 13.

25. A package containing alkaline material and formed from the film of Claim 14.

26. A package containing alkaline material and formed from the film of Claim 16.

27. A package containing alkaline material and formed from the film of Claim 18.

28. A package containing alkaline material and formed from the film of Claim 20.

29. A package containing alkaline material and formed from the film of

Claim 22.