AU684827B2

AU684827B2 - Wax-containing release agent for thermally transferable inscription and decoration systems

Info

Publication number: AU684827B2
Application number: AU75990/94A
Authority: AU
Inventors: Franz-Leo Dr. Heinrichs; Gerd Dr. Hohner; Klaus Dr. Rieger
Original assignee: Hoechst AG
Current assignee: Hoechst AG
Priority date: 1993-11-13
Filing date: 1994-10-21
Publication date: 1998-01-08
Anticipated expiration: 2014-10-21
Also published as: AU7599094A; CZ278294A3; BR9404423A; TW375623B; RU2115561C1; ZA948960B; DE4338879A1; RU94040391A; CA2135593A1; EP0654487A1; KR950014203A; JPH07233292A

Description

Our Ref: 528230 P/00/011 Regulation 3:2

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT o o *fl.

a. a° a a a. as oo ft te o a r a a Applicant(s): Hoechst Aktiengesellschaft D-65926 FRANKFURT AM MAIN

GERMANY

ooio o Address for Service: Invention Title: DAVIES COLLISON CAVE Patent Trade Mark Attorneys Level 10, 10 Barrack Street SYDNEY NSW 2000 Wax-containing release agent for thermally transferable inscription and decoration systems The following statement is a full description of this invention, including the best method of performing it known to me:- 5020 I Description Wax-containing release agent for thermally transferable inscription and decoration systems The invention relates to a wax-containing release agent for thermally transferable inscription and decoration systems, which contains a certain copolymer as the main component.

Processes which are based on the fact that an image printed on a film support is transferred by the use of heat to the article to be decorated or to be inscribed have been known for many years for the decoration and inscription of many articles of daily use. A heatactivatable adhesive layer which, in the multilayer transfer system, comes into direct contact with the article to be decorated is required for fixing the characters to be transferred. A thin but therefore very efficient release layer is required for ensuring that, after transfer, the film support or the paper support can 20 be satisfactorily separated from the characters, which are generally protected by a protective lacquer.

Various transfer processes, the structure of such systems and different release layers form the subject of many ego••: patents and applications (cf. US 2 862 832, US 2 984 413, US 2 990 311).

Wax-like r. .pounds having different compositions are frequently described for the formation of effective release layers. In addition to nonpolar, simple hydrocarbon waxes, oxidation products prepared by oxidizing such products are also used. Furthermore, the exceptionally good release effect of soap-containing waxes has long been known. A particularly effective release layer contains predominantly partially hydrolyzed montan ester waxes mixed with other waxes (cf. US 3 616 015).

2 Soap-containing waxes, including those based on montan wax, frequently have a slight natural color and tend to yellow.

Since, after the transfer process, traces of the very thin release layer remain on the article to be decorated, the users of these transfer systems have long desired that these trace residues remain invisible and are not noticeable as an unpleasant discoloration even on prolonged exposure to sunlight.

It is also known that the release coating, which generally extends on all sides beyond the printed image to be transferred, produces, on the article to be decorated, a faintly visible halo effect which in the case of wax-containing release coatings yellows in the 15 course of time and can be seen in particular in the case of transparent hollow objects, for example plastics bottles.

It was therefore the object to find release agents which should have a very light color (virtually no natural 20 color) in combination with high transparency and little tendency to yellow.

It has now been found that this object can be achieved by the use of certain copolymers.

The invention therefore relates to a wax-containing release agent for thermally transferable inscription and decoration systems, essentially comprising a copolymer of to 99.5 parts by weight of units which are derived from a C 12 -C,,-a-olefin, 0.1 to 50 parts by weight of units which are derived from a carboxylic acid of the formula CH 2

=CR'-COOH,

0.1 to 60 parts by weight of units which are derived from a carboxylic ester of the formula CH 2

=CR

1

-COOR

2 in these formulae R 1 being a hydrogen atom or a methyl group and R 2 being a straight-chain or 3 branched alkyl radical having 1 to 6 carbon atoms, and 0.0 to 30 parts by weight of units which are derived from styrene, 3-methylstyrene, 4-methylstyrene or amethylstyrene.

The release agent according to the invention essentially comprises a copolymer of a-olefins, unsaturated carboxylic acids and unsaturated carboxylic esters.

Suitable a-olefins are those having a chain length of 12 to 60, preferably 18 to 60, particularly preferably 24 to carbon atoms. Both olefins having only one type of chain and olefin mixtures such as those obtained as distillation cuts or distillation residues, for example in the known production processes, may be used. Indus- 15 trial -olefin mixtures, in particular those having a relatively long chain length, may contain greater or smaller amounts of internal and pendant olefinic double bonds (vinylidene and vinylene groups), in addition to 1alkenes.

Compounds of the formula CH 2

=CR

1 -COOH, in which R 1 is a hydrogen atom or a methyl group, for example acrylic or methacrylic acid, are used as unsaturated carboxylic acids for the copolymers to be used according to the invention. Compounds of the general formula S 25 CH 2

=CR

1

-COOR

2 in which R 1 has the above meaning and R 2 is a straight-chain or branched alkyl radical having 1 to 6 carbon atoms, are used as unsaturated carboxylic esters.

The methyl and ethyl esters of acrylic and methacrylic acid are preferred, and the methyl ester of acrylic acid is particularly preferred.

The copolymers to be used according to the invention are prepared in a manner known per se, by reacting the starting monomers under the catalytic action of small amounts of organic peroxides in the presence or absence of an inert solvent. Polymerization in the absence of a 4 solvent is preferred. For example, a mixture of carboxylic acid, carboxylic ester and free radical initiator may be added dropwise to initially taken a-olefin while stirring at an elevated temperature.

After the end of the reaction, unconverted monomers and volatile decomposition products of the peroxide can be separated off by distillation. Organic peroxides are preferably used as free radical initiators. Here, the reaction temperature must be adapted to the decomposition characteristics of the particular peroxide us d. At a temperature of 100 to 160°C, for example, dialkyl peroxides, such as di-tert-butyl peroxide, or diaroyl peroxides, such as dibenzoyl peroxide, are suitable. The molar ratio of the monomer components and hence the chemical composition and the polarity of the copolymers can be varied within wide limits. It is thus possible to adapt the properties of the release agent in an optimum manner to the particular application requirements.

The monomers are used in the following ratios: a-olefin 20 to 99.5, preferably *40 to 95, by weight unsaturated carboxylic acid 0.1 to 50, preferably to 30, by weight **ee unsaturated carboxylic ester 0.1 to 60, preferably 25 1.0 to 40, by weight The reaction temperature is 70 to 180°C, preferably 90 to "160°C, and the reaction pressure is 1.0 to 5.0, preferably 1.0 to 1.5, bar. The reaction time is preferably 1 to 7 hours.

In addition to the copolymer, the release agent according to the invention may also contain resins, further waxes and elasticizers. The copolymer content is up to 100% by weight, preferably 40 to 60% by weight.

The copolymer to be used according to the invention, which in particular is soap-free, exhibits not only I'VI'IC'Al SPl C l'Wi excellent colour stability during exposure to heat but in particular a release action which corresponds to the values of soap-containing montan waxes.

The invention further provides a method of transfer printing wherein an inscription and/or decoration system is thermally transferred to an article to be inscribed and/or decorated. The method utilises a wax-containing release agent essentially comprising a copolymer of 20 to 99.5 parts by weight of units which are derived from a C,,-Co,-c-olefin, 0.1 to 50 parts by weight of units which are derived from a carboxylic acid of the formula CH 2 =CRI-COOH, 0.1 to 60 parts by weight of units which are derived from a carboxylic ester of the formula CH 2

=CRI-COOR

2 where, in these formulae, R 1 is a hydrogen atom or a methyl S 15 group and R 2 is a straight-chain or branched alkyl radical having 1 to 6 carbon atoms, and 0.0 to 30 parts by weight of units which are derived from styrene, 3-methylstyrene, 4methylstyrene or a-methylstyrene. The method is carried out in accordance with the known practice of the art.

The Examples which follow are intended to illustrate the invention. Examples 1 to 4 illustrate the release agent and S Example 5 the method of transfer printing utilising the release agent. Acid and saponification values and dropping points were determined by the DGF standard methods M-IV 2 (57) and M-III 3 respectively (standards of the Deutsche Gesellschaft fir Fettwissenschaft e.V. [German Society for Fat Science]). The melt viscosity was measured with the aid of a rotational viscometer.

2. 997 Example 1 Preparation of a C 2 4

-C

6 o-a-olefin/acrylic acid/methyl acrylate copolymer 500 g of a commercial C 24 -C,-a-olefin cut were initially taken in a five-necked flask equipped with a thermometer, a stirrer, a dropping funnel and a reflux condenser and were heated to 140 0 C. At this temperature, a mixture of 219.0 g of methyl acrylate, 10.0 g of acrylic acid and g of di-tert-butyl peroxide was added dropwise while stirring in the course of 5 hours. After the end of the dropwise addition, the mixture was allowed to continue reacting for a further 30 minutes, and volatile components were distilled off in vacuo at about 15 mbar and S 15 at a bath temperature of 170 C. The colorless reaction product which solidified to a wax-like substance was poured into trays.

Characteristics: acid value 11 mg KOH/g, saponification value about 160 mg KOH/g, dropping point 70 0 C, melt 20 viscosity 520 mPa.s (measured at 900C)

V

6 Example 2 Preparation of a 1-tetradecene/acrylic acid/methyl acrylate copolymer In a process analogous to that described in Example 1, 196.0 g of 1-tetradecene, 131.7 g of methyl acrylate, g of acrylic acid and 2.6 g of di-tert-butyl peroxide were reacted with one another. The resulting colorless, semisolid terpolymer had an acid value of 10 mg KOH/g and a saponification value of about 205 mg KOH/g.

Example 3 Preparation of a soap-containing ester of a C 24 -Co-aolefin/chromic acid oxidation product Preparation of the oxidation product 100 kg of a C 30 +-a-olefin were heated to 100 0 C and 1250 dm 3 of a solution of Cr0 3 in sulfuric acid (content about 100 g/dm 3 were added. The mixture was stirred until the oxidizing agent had been consumed. The organic phase was separated off, washed and dried. A mixture of long-chain carboxylic acids having an acid value of 125 was obtained.

Preparation of the experimental product kg of the abovementioned oxidation product were introduced into the reactor, 4,9 kg of 1,3-butanediol were added and the mixture was heated to 100°C. At this temperature, 200 g of 70% strength methanesulfonic acid were added as a catalyst. The temperature wai increased to 125 0 C. The mixture was stirred while blanketing with

N

2 and distilling off the water of reaction, until the acid value had decreased to 51. The catalyst was then neutralized by adding 80 g of Ca(OH) 2 1850 g of Ca(OH) 2 were then added to neutralize the product. The mixture was stirred while distilling off 7 the water of reaction, until the acid value had decreased to 15-20. The batch was then bleached with H202,, dried and filtered.

Characteristics: Acid value 17 mg KOH/g, saponification value 94 mg KOH/g, dropping point 103°C, melt viscosity about 50 mPa.s (measured at 140°C) Example 4 In order to test their heat stability (discoloration), the waxes prepared according to Examples 1 to 3 were subjected to a heat treatment at 180 0 C for 6 hours, both in the presence of air and under a CO 2 inert gas atmosphere. It was found that the copolymers according to Examples 1 and 2 withstood the heat test with substantially less discoloration, the presence or absence of atmospheric oxygen evidently having no effect. However, the best result was obtained with a copolymer according to Example 1, which showed almost no tendency to yellow after exposure to heat for 6 hours.

In order to determine the release effect under laboratory 20 conditions, the waxes were applied in the form of a melt to coated and satinized paper (matt 115 g art paper) with the aid of a 6 itm knife coater using a simple laboratory coater (the K-Control Coater from R.K. Chemical Corp.

Ltd., Royston, Herts., UK). Smooth coatings having different levels of high gloss resulted.

cm wide self-adhesive tape was stuck onto the wax layer with the use of a roller. The test sample thus produced cm x 17 cm) was subjected to a peel test (190 0 C) in an Instron tensile tester. Peeling rate: 200 m/minute, clamped length: 25 mm.

For comparison, identical coatings were produced using soap-containing montan waxes. The known calciumcontaining montan ester waxes having the following _I I_ P:\WPDOCStAL\S.CiiIi(r'lSJi'irn characteristics can serve as examples of soap-containing montan waxes: Dropping point about 102 0 C; acid value about 12mg KOH/g, saponification value about 110 mg KOH/g; density about 1.02 g/cm 3 drawing hardness about 300 bar/23 0

C.

Peel Test Wax from Example 1 3.3 N/5 cm Wax from Example 3 4.9 N/5 cm Wax from Example 4 4.0 N/5 cm Example Transference of pattern, and inscription of article.

An art paper was coated with the copolymer of Example 1 by means of a laboratory coater. A pattern was printed on the wax layer using a laboratory printing machine (offset printing machine from Prafbau Corp.) and a commercial offset printing ink ("Novaboard Cyan 4C" from 20 Kast Ehinger Corp.). After drying the ink, the coated and printed paper was positioned with its printed side on a smooth and colourless PVC surface. By applying pressure by means of a metal plate heated to about 170 0 C, the printed pattern and the wax layer were transferred to the PVC surface. The resulting printed image was of excellent quality.

Note With the exception of Example 5 and the descriptive passage immediately preceding Example 1 (where a method-defining paragraph has been inserted and the two short original paragraphs have been incorporated into an expanded replacement paragraph), the description of the specification is otherwise unamended. It has been retained as filed to preserve the fullness of the original disclosure. The scope of the invention is defined in the proposed amended ensuing claims.

4 T j

Claims

1. A method of transfer printing wherein an inscription and/or decoration system is thermally transferred to an article to be inscribed and/or decorated, characterised in that there is utilised a wax-containing release agent essentially comprising a copolymer of to 99.5 parts by weight of units which are derived from a a-olefin, 0.1 to 50 parts by weight of units which are aerived from a carboxylic acid of the formula CH,=CRI-COOH, 0.1 to 60 parts by weight of units which are derived from a carboxylic ester of the formula CH =CR 1 -COOR 2 where, in these formulae, R 1 is a hydrogen atom or a methyl group and R" is 15 a straight-chain or branched alkyl radical having 1 to 6 carbon atoms, and 0.0 to 3Q parts by weight of units which are derived from styrene, 3-methylstyrene, 4-methylstyrene or a-methylstyrene. S"

2. A method as claimed in claim 1, wherein the a-olefin is a to Co 6 -a-olefin.

3. A method as claimed in claim 1, wherein the a-olefin is a C1 4 to C,-a-olefin. 25

4. A method as claimed in claim 1, wherein the carboxylic ester of the formula CH,=CR'-COOR 2 is an ester in whose formula R is a hydrogen atom or a methyl group and R 2 is a methyl or ethyl group. A method as claimed in claim 1, which contains 40 to 60% by weight of the copolymer. DATED this 10th day of September, 1997. HOECHST AKTIENGESELLSCHAFT By Its Patent Attorneys DAVIES COLLISON CAVE yT. 0 Abstract of the Disclosure Wax-containing release agent for thermally transferable inscription and decoration systems A highly effective release agent for thermally transfer- able inscription and decoration systems contains a copolymer as the main component. The copolymer to be used according to the invention, which in particular is soap-free, exhibits not only excellent color stability during exposure to heat but in particular a release effect which corresponds to the values of soap-containing *montan waxes. a* zi