CA2172223A1

CA2172223A1 - Hot-melt adhesive composition for the coating of interlining material

Info

Publication number: CA2172223A1
Application number: CA002172223A
Authority: CA
Inventors: Ulrich Simon; Siegfried Hahn
Original assignee: Huels AG
Current assignee: Huels AG
Priority date: 1995-03-22
Filing date: 1996-03-20
Publication date: 1996-09-23
Also published as: TW343230B; CN1134966A; DE19510315A1; CZ83496A3; US5677038A; JPH08259906A; PL313402A1; CZ285347B6; EP0733691A3; EP0733691A2; KR960034351A

Abstract

Disclosed is a sheet structure coated thereon with a hot-melt adhesive composition which comprises: a base layer, and a top layer comprising at least one thermoplastic hot-melt adhesive and an epoxide, wherein the epoxide is contained in an amount of from 5 to 25% by weight based on dry weight of the top layer. The sheet structure is typically an interlining material for clothing. Also disclosed is a method of producing the coated sheet structure by applying an aqueous paste of a hot-melt adhesive composition as a base layer, scattering powder of a hot-melt adhesive composition containing the epoxide and vibrating the sheet structure to remove the powder that does not adhere. By the use of the epoxide, it is possible to prepare cleaning-resistant laminated materials which have a particularly high wash resistance.

Description

~ ~ 2172223 O.Z. 4931 Hot-melt adXesive com~osition for the coatinq of inter-lininq material The invention relates to a hot-melt adhesive composition for the coating of sheet structures, for examples tex-tiles, leather, foam materials or polymer films. Theinvention relates in particular to a hot-melt adhesive composition for the coating in a pattern of bondable interlining materials for the clothing industry, espe-cially for outer clothing.

Hot-melt adhesive compositions are known which are preferably applied in a pattern, in the form of an aqueous paste, to a sheet structure to be coated. Drying and sintering are then carried out. The sintered product constitutes the hot-melt adhesive composition. The coated sheet structures are laminated, in sheet form or cut to shape, with other sheet structures in sheet form or cut to shape, under the action of pressure and a compara-tively mild temperature to give cleaning-resistant laminates having a particularly high degree of wash resistance and adhesion.

Numerous hot-melt adhesive compositions having cleaning-resistant properties are known for the screen-printing technique. These are principally formed from aqueous-pasty mixtures comprising fine hot-melt adhesive powders, which can also be employed per se, in coarser granular form, directly for coating by the scatter or powder dot method. The cleaning-resistant hot-melt adhesive composi-tions most in use today are based on copolyamides, copolyesters or low-pressure polyethylene. Other hot-melt adhesive compositions which are likewise used are not resistant to cleaning.

To form a paste from the fine hot-melt adhesive powders, in order to produce the adhesive layer, special suspen-sion agents or dispersants are used which allow the ` ,~- 217222:~

- 2 - O.Z. 4931 pastes to be printed cleanly without reducing the resis-~tance to cleaning. In addition, dispersants are intended to give rise to particular features in terms of proper-ties, for example the prevention of sedimentation of the powders incorporated by mixing, a print with well-defined contours, controlled penetration of the hot-melt adhesive paste, prevention of penetration by the outer material, the avoidance of recoiling in the course of bonding, or the prevention of the edges becoming welded together while the sheet structures are being cut to shape.
Examples of such dispersants have been described, for example, in patents D~-B 20 07 971, DE-B 22 29 308, ~E-B 24 07 505, DE-B 25 ~7 504 and DE-B 35 10 lO9.
Plasticizers can be added to the dispersants. In many cases, further additives comprising high molecular weight polyethylene oxide are added, which increase the spreadability of the paste.

For coating in a pattern by the screen-printing techni-que, screen-printing stencils are used which have a regular or i-reqular arrangement of perforations through which hot-melt adhesive compositions are pressed onto the interlining material using an internal doctor blade.
Whereas, formerly, screen stencils were used which had a comparatively wide spacing and large apertures, for example 17 mesh, in recent times coatings of increasing fineness have been carried out with a close sequence of smaller apertures, for example 30 mesh, with the forma-tion of small, closely adjacent dots of hot-melt adhe-sive. Moreover, the interlining materials have become more lightweight, finer and more open. The problems associated with coating have grown as the patterns have become finer, and the cleaning and washing problems have increased simultaneously, since the larger pattern arrangement with larger individual dots produced a greater adhesive strength than the finer pattern arrange-ment with relatively small individual dots.

However, the use of interlining materials has also 217222~
~ ~.

- 3 - O.Z. 4931 experienced a gradual change. For reasons of fashion and, - probably, of environmental protection as well, there is increasing use in articles of clothing of interlining materials which have been washed rather than cleaned, for example interlinings for leisure wear.

This change in trends has led to the copolyamide hot-melt adhesives which were originally used exclusively for article~ of outer clothing being replaced more and more by copolyesters, since copolyesters - although not having the particularly good dry-cleaning resistance of the copolyamides - nevertheless possess a better resistance to washing. Low-pre~sure polyethylenes are excluded because of the excessive bonding temperatures.

Costs and quality issues have dictated a marked reduction in the quantity of coating which is applied per m2 of interlining material. Whereas, formerly, add-ons of from 18 to 25 g/m2 were common, they are nowadays from 7 to 15 g/m2, to meet the need for a soft, flowing drape of the bonded articles of clothing.

In order to solve the problems relating to the reduced washing and cleaning resistance and to the weaker adhesion, improved hot-melt adhesive compositions and also improved coating technologies were developed. Dual-dot or double-dot coatings are described, for example, in patents DE-B 22 14 236, DE-B 22 31 723, DE-B 25 36 911 and DE-B 32 30 5,9. Moreover, patents EP-A 0 21g 376 and EP-A 0 365 711 describe an indirect coating method.

The coating substrates were improved by using finer yarns having individual fibres of finer denier, ranging down to the microfibre region, and synthetic yarns, for example high-bulk acrylic yarns and crimped polyester yarns.
Moreover, the fabrics originally used ha~e been replaced by other sheet structures, for example by weave-knit products or by weave-~nit bonded fibre webs and stitch-bonded webs, the latter materials representing a - 4 - O.Z. 493 combination of bonded fibre webs with knitted fabrics.

Deficiencies which continue to exist are seen, in part~-cular, in a stiffening and in a reduced crease-resistance of a bonded laminate of interlining and outer material, -especially in the case of finely patterned coatings. A
factor regarded as being particularly negative, however, is that, in fine-coated interlining materials on fine outer materials, for example blouse outer materials, and despite the u~e of polyesters, the wash resistance of the ~onded laminate is no more than moderate and in many cases is even deficient. There therefore continues to be a considerable need for an interlining of low coating weight which can be applied by hot pressing at the mild fixing temperatures which are nowadays conventional and - lS which imparts a soft bonded handle, can be washed without any problems and retains a high adhesive strength after the washing procedure.

There is a great need for such interlinings in women~s outer wear. Here in particular, depending on fashions, outer materials which lend themselves very unreadily to bonding, such as silk, polyester-viscose-georgette and siliconized or fluorocarbonized outer materials, are processed. The current interlinings achieve very good primary adhesion, but after washing or cleaning complete - 25 detachment occurs.

Even complex coating methods such as the traditional double dot and indirect coating techniques bring hardly any success in this context.

An object of the invention is therefore to find a hot-melt adhesive composition which, with a reduced coating amount, has a high adhesive strength and outstanding resistance to washing and cleaning. The adhesive composi-tion may be applied to nonwovens, charmeuse and weave-knit fabrics, primarily to interlinings with weights of from 15 to 40 g/m2, preferably interlinings which have 217222~

been pretreated with silicones or silicone plasticizers. The hot-melt adhesive aomposition should in this context be able to be used in particular for double dot coating.
It has now surprisingly been found that a hot-melt adhesive composition consisting of a base layer and an over-lying top layer comprising a thermoplastic hct-melt adhesive and an epoxide meets this requirement. The epoxide content in the top layer here is from 5 to 25% by weight. The thermo-plastic hot-melt adhesive in the top layer may be a copolyester, a copolyamide or of both components. Preferred epoxides are those based on bisphenol A epoxide in particular.
The epoxide preferably has a melting point of 65 to 110C, particularly preferably a melting point of from 95 to 110C, an epoxide equivalent of from 450 to 6,000 g/equivalent, preferably from 2,400 to 4,000 g/equivalent, and a particle size of from 1 to 80 ~m. The proportion of epoxide is from 5 to 25~ by weight, based on the dry weight of the top layer.
The top layer may preferably have the following compositions:
from 0 to 25% by weight of a copolyamide, from 50 to 95% by weight of a copolyester and from 5 to 25% by weight of the epoxide.
The hot-melt adhesive composition in the case of double dot coating is applied, in accordance with the invention, to the sheet structure to be coated, for example an interlining for an article of clGthing, preferably in such a way that first of all a hot-melt adhesive paste is applied as a base layer by the screen-printing technique. This base layer may preferably contain as adhesive composition a mixture of low-pressure 21722~3 polyethylene and a commercially available high-melting copolyamide. The weight ratio of the low-pressure polyethylene to the copolyamide in a very preferred embodiment is 60 : 40.
On top of this is applied an upper layer or top layer.
Particularly preferred as top layer is a hot-melt adhesive powder which is scattered on. After it has been scattered on, the powder which does not adhere to the base layer is then removed, for example, by vibrating the sheet structure. The top layer according to the invention preferably contains a low-melting copolyamide in admixture with bisphenol A epoxide or a low-melting copolyester in admixture with bisphenol A
epoxide.
In order to form a paste from a mixture of copoly-amide or copolyester and low-pressure polyethylene for the base layer, generally dispersants are used. Examples of such dispersants are those described in the Patent documents mentioned in the introduction, DE-B 20 07 971, DE-B 22 29 308, DE-B 24 07 505 and DE-B 35 10 109, to which express reference is made here. Particularly suitable dispersants are those based on ethoxylated fatty alcohols having 12 to 18 carbon atoms in the chain with degrees of ethoxylation of from 3 to 5 with a thickener based on polyacrylic acid or polymethacrylic acid. These dispersants are employed in the wet hot-melt adhesive paste generally in a proportion of from 0.5 to 2% by weight. The solid content of the hot-melt adhesive paste is preferably from 30 to 50% by weight. The weight ratio of the copolyamide or copolyester to the low-pressure polyethylene is not critical and is preferably 20 : 80 ~o 60 : 40.

217222~
- 6a -The top layer of the hot-melt adhesive composition according to the invention preferably contains acommercial copolyamide or copolyester. Particular preference is given here, as has surprisingly turned out to be the case, to a mixture of bisphenol A epoxide and a low-melting copolyester or a mixture of a bisphenol A epoxide and a copolyamide. The top layer is preferably scattered as a powder mixture onto the base layer. Preferably the mixture predominantly has a particle size of from 80 to 160 ~m. The weight ratio(on a dry basis)of the base layer to the top layer is preferably 3 : 1 to 1 : 3.
The copolyamides or copolyesters are generally well-known in the art and include commercial products, for example VESTAMELT X 7352, VESTAMELT 730, VESTAMELT 4581 from Huls AG. Critical for the application according to the invention is the proportion of the epoxide.

*

Trade-mark - 7 - O.Z. 4931 Example of double dot coatinqs The top coat of the hot-melt adhesive composition accord-ing to the invention preferably contains a copolyamide, copolyester or mixtures thereof. Particular preference is given here, as surprisingly turned out to the be case, to the use of a mixture of copolyester with a bisphenol A
epoxide or of a mixture of copolyamide and a bisphenol A
epoxide. The top layer is preferably scattered onto the base layer, the top layer being a powder. The mixture predominantly has a particle range of from 80 to 160 ~m.
In the two-layer coating of hot-melt adhesive paste and powder, the weight-ratio of hot-melt adhesive paste (dry) to top-layer powder is about 1 : 1.

The hot-melt adhesive paste used as base layer has the following composition:

Water 6.30 parts by weight Mirox*HP 0.15 part by weight (polyacrylic acid derivative) INTRASOL*1218/5 0.30 part by weight (ethoxylated fatty alcohol) VESTAMELT 751-P1 1.00 part by weight Schattifix 1820-P1 1.50 parts ~y weight The copolyamide employed is VESTA~ELT 751-Pl from Huls AG:

VESTAMELT 751-Pl Particle size 1 to 80 ~m Melt index (160C, 21.6 N) 14 g/10 min m.p., melting-point tube 108C
m.p., DSC 98C

The low-pressure polyethylene used to produce the paste is defined as follows:

Trade-mark - 2~ 72223 _ ~ _ o.z. 4931 LP-polyethylene: Schattifix 1820-Pl 2article size 1 to 80 ~m ~elt index (l90~C, 21.6 N) 20 g/10 min ~ ~elting point 130C
~anufacturer: Schatti, CH

The paste additives are stirred together in the sequence given above. The paste is applied to a coating substrate through the perforations of a 25 mesh screen stencil with regular dot arrangement, using an internal doctor blade.
The coating substrate is a stitch-bonded nonwoven of 30 g/m2 made from PES/PA fibres (30 : 70). The nonwoven has PES warp multifilaments knitted through it. The paste add-on is from about 5 to 6 g/m2 when dry. After coating, the wet base layer is scattered with the powder mixture - 15 according to the invention comprising copolyester and epoxide.

The top layer is a mixture of the copolyester VESTAMELT 4581 (9o ~ by weight) and a bisphenol A epoxide (10 % by weight) having an epoxide equivalent of from 2 400 to 4 000 and a softening point (Rofler) of from 100 to 110C. The add-on by scattering is from about 5 to 6 g/m2.

After the base layer has been covered with scattered material, the nonwoven is set in vibration using a high-speed rotary beater mechanism. The p~wder which does not adhere to the wet base layer is removed by blowing it off and extracting it by suction. Drying and sintering are then carried out. The finished interlining is then bonded to an outer material and the adhesive strength is measured.

ComParison examPle As comparison example, the base layer is applied in the above manner. The top layer applied by scattering, however, is only the copolyester, with no epoxide.
Following extraction by suctionj drying and sintering, *

Trade-mark _ g _ o.Z. 4931 adhesion measurements are carried out.

Evaluation:

Specimen from O~ter after 1 x ~ashing 3 x ~C
material bonding at 40C
Example silk 6.5 5.5 6.5 polyester georgette 5.8 4.5 6.0 Comparison example silk 4.0 0.8 fell prior art apart polyester 2.5 0.3 fell georgette apart The interlining according to the invention, with epoxide, displays a markedly better adhesion after washing and cleaning to outer materials which are difficult to ~ond.
The severe drop in adhesion values after washing and cleaning is very much in evidence in the case of the comparison example.

Claims

1. A sheet structure coated thereon with a hot-melt adhesive composition which comprises:
a base layer, and a top layer comprising at least one thermoplastic hot-melt adhesive and an epoxide, wherein the epoxide is contained in an amount of from 5 to 25% by weight based on dry weight of the top layer.

2. A sheet structure according to claim 1, wherein the hot-melt adhesive comprises at least one member selected from the group consisting of a thermoplastic copolyamide hot-melt adhesive and a thermoplastic copolyester hot-melt adhesive.

3. A sheet structure according to claim 2, wherein the top layer comprises:
from 0 to 25% by weight of the copolyamide, from 50 to 95% by weight of the copolyester, and from 5 to 25% by weight of the epoxide.

4. A sheet structure according to any one of claims 1 to 3, wherein the epoxide is a bisphenol A epoxide.

5. A sheet structure according to any one of claims 1 to 4, wherein the epoxide has a melting point of from 65 to 110°C, an epoxide equivalent of from 450 to 6,000 g/equivalent and a particle size of from 1 to 80 µm.

6. A sheet structure according to claim 5, wherein the epoxide has a melting point of from 95 to 110°C, an epoxide equivalent specifically of from 2,400 to 4,000 g/equivalent and a particle size of from 1 to 80 µm.

7. A sheet structure according to any one of claims 1 to 6, wherein the base layer comprises a thermoplastic copolyamide hot-melt adhesive and low-pressure polyethylene.

8. A sheet structure according to any one of claims 1 to 7, which is an interlining material for clothing.

9. A method of coating a sheet structure with a hot-melt adhesive composition, which comprises:
applying an aqueous paste of a hot-melt adhesive composition on the sheet structure as a base layer by the screen-printing technique, scattering powder of a hot-melt adhesive composition comprising at least one thermoplastic hot-melt adhesive and an epoxide as a top layer on the base layer, wherein the epoxide is contained in an amount of from 5 to 25% by weight based on dry weight of the top layer, and removing the powder that does not adhere to the base layer.

10. A method according to claim 9, wherein:
the hot-melt composition of the base layer consists essentially of (1) at least one member selected from the group consisting of a thermoplastic copolyamide hot-melt adhesive and a thermoplastic copolyester hot-melt adhesive and (2) low-pressure polyethylene, and the hot-melt composition of the top layer consists essentially of at least one thermoplastic hot-melt adhesive selected from the group consisting of copolyamides and copolyesters and a bisphenol A epoxide, wherein the bisphenol A epoxide is 5 to 25% by weight based on dry weight of the top layer.

11. A method according to claim 10, wherein:
the aqueous paste applied as the base layer also contains a dispersant and has a solid content of 30 to 50% by weight.

12. A method according to any one of claims 9 to 11, wherein the powder of the hot-melt adhesive composition applied as the top layer has a particle size of 80 to 160 µm.

13. A method according to any one of claims 9 to 12, wherein the epoxide has a melting point of 65 to 110°C, an epoxide equivalent of from 450 to 6,000 g/equivalent and a particle size of from 1 to 80 µm.

14. A method according to any one of claims 9 to 13, wherein the hot-melt adhesive composition of the top layer consists essentially of from 0 to 25% by weight of a thermo-plastic copolyamide hot-melt adhesive, from 50 to 95% by weight of a thermoplastic copolyester hot-melt adhesive and 5 to 25%

by weight of the epoxide.

15. A method according to any one of claims 9 to 14, wherein the sheet structure is an interlining material for an outer clothing and the hot-melt adhesive composition is coated in a pattern; and wherein the coated hot-melt adhesive composition is further subjected to drying and sintering.