GB2469908A

GB2469908A - Transfer composition comprising isobutyrate and acrylic

Info

Publication number: GB2469908A
Application number: GB201006835A
Authority: GB
Inventors: Mark Takacs
Original assignee: Sericol Ltd
Current assignee: Sericol Ltd
Priority date: 2009-04-23
Filing date: 2010-04-23
Publication date: 2010-11-03
Anticipated expiration: 2030-04-23
Also published as: GB0906969D0; GB2469908B; GB201006835D0

Abstract

The transfer printing composition comprises an acrylic resin and an isobutyrate plasticiser. The preferred composition comprises 10-40 (20-30) wt% acrylic resin, 10-50 (25-40) wt% isobutyrate plasticizer, 1-25 (10-15) wt% hot melt resin, especially polyester and polyether, 1-25 (10-15) wt% white pigment and 1-25 (2-10) wt% another plasticiser. The composition is used for producing an image on textile garments, transfer printing. A coloured ink is applied to a carrier substrate, preferably paper by lithographic printing. The composition is then applied, preferably to the dried ink by screen printing and heat set.

Description

Transfer composition This invention relates to transfer printing and in particular to a transfer composition suitable for transferring a printed image.

Transfer printing is a variant of textile printing. The inks to be applied are printed as a reverse image onto a carrier sheet, which may be paper or some other material such as PET. Each colour ink is heat set, but not fully cured, before the next colour is applied to the carrier sheet. An adhesive is usually applied after the colours, which again is heat set. The printed sheets are then relatively stable and can be moved around and applied to textiles and garments, (e.g., items made of cloth, tee shirts, jeans and jackets) over a prolonged period of time. When the printed sheet is placed on top of a garment under a heat transfer press, the adhesive and the colours are transferred from the carrier sheet onto the garment. Garments printed in this way have good resistance properties. Transfer printing is popular because it allows a printer to keep prints for a period of months or even years without transferring them onto the garment.

Litho transfers' are a particular type of transfer printing, whereby the coloured inks are applied to the carrier sheet by a lithographic process to produce an image in reverse and then a white adhesive is applied to the back of the print via screen printing, and then heat set. When placed under the transfer press the adhesive transfers onto the garment, carrying the lithographic inks with it, while any colour that is not covered by the adhesive remains on the carrier sheet.

Lithographic inks used are specially formulated for this transfer process. The most commonly used ink is the Texlith range, from Gibbon Marler, and the most commonly used carrier sheet is T75 siliconised transfer paper, from Arjo Wiggins.

A typical transfer schedule for litho transfers is 180 °C for 12 seconds, using medium pressure to adhere the transfer to the garment.

In the production of litho transfers, printing the colours using a lithographic press allows the colours to be applied more quickly than would be possible using a screen process. The artwork produced by the lithographic process is also finer and photographic quality images can more easily be reproduced.

The adhesive is white rather than clear and this is why it is not necessary to apply a lithographic white ink when the printed image is being produced. Any areas of white in the image rely on the white adhesive being seen, rather than a separate white colour. This also means that the four-colour process inks, which are inherently transparent, do not have to be printed over a white to give them opacity.

For litho transfers, there is generally a narrow "window of opportunity" to print the adhesive onto the back of the litho colours. If the adhesive is applied too soon the lithographic inks are too wet and rub fastness and wash resistance are poor. If too long a time is left between printing the lithographic inks and applying the adhesive, then the inks may become too dry, colour transfer is reduced and wash fastness and rub are again impaired. The ideal time for transfer is generally between 3 and 8 days after the printing of the lithographic inks. However, this time is ultimately dependent upon the formulation of the inks and the way they are printed.

Plastisol adhesives comprise a suspension of resin in a plasticizer. Plastisol adhesives do not dry unless heated to a temperature approaching 100 °C and this means that these adhesives do not dry out during the screen printing process and screen stability is therefore excellent. Also, plastisol adhesives do not require catalysts and so can be taken off the screen and re-used.

Historically, plasticizers employed in the adhesives used in this process have generally been phthalate esters and the resins employed are almost exclusively PVC-based. Both these chemical types have environmental concerns and in recent times both have come under increased pressure from an environmental point of view However, while it is common for adhesives to contain plasticizers other than phthalate-esters, PVC is still by far the most common resin used for these types of adhesives.

While there are PVC-free adhesives available, these tend to be based on water-based acrylic or polyurethane dispersions. However, these types of adhesive dry while being printed, meaning that screen stability is worse than plastisol adhesives. Also, these resins require use of a catalyst to cross-link them for increased wash resistance and this further reduces the screen stability, and also means that adhesive cannot be re-used once a catalyst has been added.

Water-based adhesives contain volatile solvents such as water that do not become part of the printed film and so the level of solids in the resultant printed film is lower than that as compared to when plastisol adhesives are employed. It logically follows that the opacity of water based adhesives tend to be lower and that multiple print layers are required to give the same opacity.

Resins for use in water-based adhesives tend not to be thermoplastic, and so once coalesced on the carrier sheet they may not re-melt when heated. Thus there is a requirement for the addition of a hot-melt resin to give adhesion to the fabric. This is addition of hot-melt resin increases the solids of the system, which limits the amount of white pigment (used to give opacity) that can be included in the adhesive. This leads to the fact that there is often a requirement that a specialist adhesive needs to be printed after the white layers have been applied to the carrier sheet. If the hot melt resin is not present in the adhesive film, the film will not melt into the fabric and so adhesion will be poor.

One aim of the invention is to formulate a plastisol transfer adhesive that works with traditional lithographic inks and transfers papers to give good adhesion and/or wash resistance.

Another aim of the invention is to formulate a plastisol transfer adhesive that works with traditional lithographic inks and transfer papers to give good adhesion / wash resistance but does not contain PVC or phthalate plasticizers.

Accordingly, the present invention provides a composition for transferring a printed image onto a substrate comprising one or more of an acrylic resin and isobutyrate plasticizer.

The present invention also provides a composition comprising an acrylic resin and isobutyrate plasticizer.

The compositions of the present invention are suitable for use as transfer adhesives in a transfer printing process. The compositions of the invention are compatible with lithographic inks and have good film-forming properties on paper and textile substrates.

The composition of the invention preferably comprises 10-40 wt% acrylic resin and 10-50 wt% isobutyrate plasticizer, based on the total weight of the composition, more preferably 20-30 wt% acrylic resin and 25-40 wt% isobutyrate plasticizer.

By "acrylic resin" is meant a resin derived from the polymerisation of acrylic acid, methacrylic acid, an ester of acrylic acid, an ester of mcthacrylic acid or combinations thereof Acrylic resins are widely available and well known to the person skilled in -the art.

Acrylic resins in general do not have affinity for the lithographic inks, unlike PVC resins which have a degree of receptivity in their own right. This means that it is vitally important that the resin coalesces fully with the plasticizers used. Any plasticizer lost from the film would reduce the amount of lithographic ink the adhesive film could support, resulting in reduced wash resistance and rub fastness.

tn one embodiment of the present invention the composition additionally comprises a hot melt resin.

The acrylic resin used in the composition of the present invention is thermoplastic.

Thus the hot-melt resin is an additional resin, giving increased adhesion to the fabric.

Hot melt resins, particularly polyesters, have been found to have affinity for lithographic inks.

Suitable hot melt resins include polycthcr resins, polyester resins and combinations thereof The hot melt resin also does not coalesce with the plasticizer fully. This means that if there is too much hot melt resin present the film will be under-bound and will lose plasticizer. This will result in impaired wash resistance / rub fastness and plasticizer migration from the film. Hot melt resins may be present in an amount 1-25 wt% based on the total weight of the composition, preferably 10-15 wt%.

In one embodiment the composition of the invention comprises a white pigment such as Ti02* The white pigment may be present in an amount of 1-25 wt% based on the total weight of the composition, preferably 10-15 wt%.

In one embodiment of the invention the composition comprises a second plasticizer that is different to the isobutyrate plasticizer. Suitable plasticizers include phosphate, polymeric, sulphonate, dibenzoate, maleate, cyclohexane, trimellitate, ethoxylate, citrate and phthalate plasticizers.

The second plasticizer is preferably present in an amount of 1 to 25 wt%, preferably 2 to 10 wt%, based on the total weight of the composition.

The present invention also provides a composition as defined above for use as a transfer adhesive in a transfer printing process.

The present invention provides a method of producing a printed sheet comprising: i) printing an ink on to a carrier substrate, and ii) applying the composition of the invention to the printed ink.

One or more coloured inks may be used to produce an image on the carrier substrate.

The image is printed as the reverse of the final image required. The ink may be heat set before the composition of the invention is applied. The ink is preferably not fully cured at this stage, however. If more than one coloured ink is applied, each colour ink may be heat set before the next colour is applied.

The ink may be applied by any suitable printing technique, for example screen printing, but is preferably applied by lithographic printing. Lithographic inks are widely available and well known to the person skilled in the art.

The composition of the invention can be applied by any suitable means but is preferably applied by screen printing. The composition may be heat set after it has been applied to the ink.

The carrier substrate can be any material that is suitable for transferring a printed image and examples include paper and plastic sheets such as PET. r

The printed sheet produced by the above method is relatively stable and can be stored before it is used to transfer the printed image to a second substrate.

The present invention also provides a method of transfer printing comprising placing the printed sheet as described above on a second substrate such that the composition of the invention is in contact with the second substrate, and applying heat and/or pressure to the printed sheet in order to transfer the composition of the invention and the ink from the carrier substrate to the second substrate.

Preferably the second substrate is a textile and can be a garment such as a T-shirt.

The compositions of the present invention can be made by simply mixing the stated components together.

Examples

We aimed to identify a blend of powdered acrylic resin and non-phthalate plasticizers that gives good affinity for the lithographic ink while forming a good film on the paper and on the garment.

The first part of this process was to establish which plasticizers were good solvents for the type of lithographic ink used. This was done by putting a drop of the plasticizer onto a fresh print and letting it soak for a few seconds. The plasticizer should have a level of solvency power such that when dropped onto the surface the ink film it can be rubbed off easily, but not so strong a solvent it would dissolve the ink film and thus pulling it off the paper (this could cause it to smudge when the image is transferred).

Various plasticizers were tested for their solvent strength and the results are shown below (graded 0-5, 0=very poor, Sexcellent): Trade name Solvency ype Supplier Reofos 95 -4 Phosphate Great Lakes Lankroflex 2307 -1 Polymeric Polyone Mesamoll -5 Sulphonate Lanxess Benzoflex 354 -3 Dibenzoate Velsicol Dioplex 702 -I Polymeric Dow DOM -5 Maleate Pentagon DINCH -5 Cyclohexane Bayer Diplast TM/ST -2 Trimellitate Lonza Beuzoflex 131 -5 Dibenzoate Velsicol Benzoflex 2088 -5 Dibenzoate Velsicol Dioplex 925 -0 Polymeric Dow Dioplex 7017 -0 Polymeric Dow Ultramoll M -0 Polymeric Lanxess Ultramoll VP -0 Polymeric Lanxess Dioplex VLV -S Polymeric Dow Lankrostat LA3 -S Ethoxylate Akcros Ultramoll III -0 Polymeric Lanxess Diplast TM7-9ST -4 Trimellitate Lonza Eastman TXIB -S Isobutyrate Eastman Lemonol AC8 -3 Citrate Multisol Polycizer As-200 -3 Polymeric DIC DIMP -5 Phthalate Univar Isobutyrate plasticizers were found to be particularly useful (e.g. Eastman TXIB).

A simple base was formulated with this plasticizer. When this base was washed straight after transfer, the flexibility and wash resistance was very good.

It was found that isobutyrate plasticizer (e.g. Eastman TXIB) mixed with acrylic resin (e.g. Dianal LP3202, from Mitsubishi Rayon), gave a good flexible film.

However 24 hours after transfer, the flexibility had reduced and wash fastness was impaired as a result because the resin had hardened. Small amounts of a secondary plasticizer were added to increase the flexibility of the film and improve wash resistance. The amount of this plasticizer added needed to be carefully controlled, as e.g. larger amounts of it could tend reduce the film's affinity for the lithographic ink and therefore also reduce wash resistance.

Table 1 below shows an example of a base formulation (base (i))

Table I

BASE (i) Chemical T No Parts Function Type Supplier Eastman TXIB 30.15 Plasticizer Isobutyrate Eastman Alkyl Pentrone Wetting Benzene A4D 0.68 Agent Sulphonate Caldie Cabosil Fumed MS 1.00 Thickener Silica Cabot Griltex Hot Melt EMS 1682E 17.32 Resin Polyester Grilon Mitsubishi LP3202 27.19 Resin Acrylic Rayon Ti02 5.00 Pigment Ti02 Kronos Table 2 gives examples of different types of plasticizers used in connection with the base in Table 1. Plasticizer was added in amounts of 2 and 5 wt%, and the performance of the resulting formulation was recorded.

BASE (i) + PLASTICIZER ____ WT% WT%

EXAMPLE EXAMPLE

_______ ___ 1 2 Base(i) WT% 98 95 Mesamoll WT% 2 5

EXAMPLE EXAMPLE

_______ ___ 3 4 Base (i) WT% 98 95 Lemonal AC8 WT% 2 5

I IEXAMPLEIEXAMPLEI

_______ ___ 5 6 Base (i) WT% 98 95 Benzoflex 2088 WT% 2 5

EXAMPLE EXAMPLE

_______ __ 7 8 Base (i) WT% 98 95 Ultramoll M WT% 2 5

EXAMPLE EXAMPLE

_______________ ______ 9 10 Base (1) WT% 98 95 Dioplex 7017 WT% 2 5

EXAMPLE EXAMPLE

_______________ _____ 11 12 Base(i) WT% 98 95 Dioplex 702 WT% 2 5

EXAMPLE EXAMPLE

_______________ ______ 13 14 Base (i) WT% 98 95 Benzoflex 354 WT% 2 5

EXAMPLE EXAMPLE

_______________ ______ 15 16 Base(i) WT% 98 95 DINA WT% 2 5

EXAMPLE EXAMPLE

______________ _____ 17 18 Base (i) WT% 98 95 Eastman 168 WT% 2 5

EXAMPLE EXAMPLE

______________ _____ 19 20 Base (i) WT% 98 95 DiOctyl Maleate WT% 2 5

EXAMPLE EXAMPLE

_______________ ______ 21 22 Base (i) WT% 98 95 Lankroflex E2307 WT% 2 5

I I I EXAMPLE EXAMPLE

______________ _____ 23 24 -Base (i) WT% 98 95 DfNP WT% 2 5

EXAMPLE EXAMPLE

_______________ ______ 25 26 Base (i) WT% 98 95 Dioplex VLV WT% 2 5 All of the above samples gave very good results for printability, peel, feel, stretch and memory. All samples also gave good results for wash. However, some samples were slightly better than others and samples 7-1 1, 13-15, were the better performers. This gives the impression that there is not a lot of difference between adding 2 or S % plasticizer. These are the samples which contain Ultramol! M, Dioplex 7017, Dioplex 702 (Z57546), Benzoflex 354 (Z575l5) and DNA (ZSSOlO).

Table 3 shows work done to determine an optimum level of secondary plasticizer in o an un-pigmented base (ii). Results were graded 0-5 as previously defined.

Table 3

BASE_(ii) _______ Eastman TXIB 39.5 Pentrone A4D 0.9 Cabosil M5 1.31 Uriltex l682E 22.69 LP3202 35.6 Total 80.25 BASE + -EXAMPLE 27 EXAMPLE 28 EXAMPLE 29 EXAMPLE 30

ADDITIONAL

PLASTICIZER (a) +

SECONDARY

PLASTICIZER (b)

-Base(ii) 80 80 80 80 EastmanTXll3 -15 10 5 0 UltramollM -5 10 15 20 Results _______________ -Transfer -4/5 4/5 4/5 3/4 Flexibility -2/3 3 4/5 4 Film Forming 4/5 4 4 2/3 Migration on 4/5 4/5 4/5 4/5 paper ___________ _______________ ________________ __________ 40°CWash 4 4 4 3 60°CWash 3/4 3/4 3 3 -EXAMPLE EXAMPLE EXAMPLE EXAMPLE 34 ___________ 31 32 33 _________ Base(ii) 80 80 80 80 EastmanTXlB 15 10 5 0 Dioplex 7017 -5 10 15 20 Results ________________ ________________ ________________ ________________ Transfer 4/5 4/5 4/5 4/5 Flexibility -4/5 4 5 4 Film Forming -4/5 4/5 4/5 4 Migration on 4/5 3 3 3 paper _______________ ______________ ______________ ______________ 40°CWash -5 5 4 4 60°CWash -3 3 2 2

-EXAMPLE EXAMPLE EXAMPLE EXAMPLE

_______________ 35 36 37 38 Base(ii) -80 80 80 80 -Eastman TXIB 15 10 5 0 DiopIex7O2 5 10 15 20 -Results __________________ ________________ ________________ ________________ Transfer -4/5 4/5 4/5 4/5 Flexibility -3 3 3/4 4/5 Film Forming -4 4/5 4 3 Migration on 3 3 3 3 paper _______________ ______________ ______________ ______________ 40°CWash 5 5 4/5 4 60°CWash 4 3/4 3 2/3

-EXAMPLE EXAMPLE EXAMPLE EXAMPLE

_______________ -39 40 41 42 Base(ii) -80 80 80 80 Eastman TXIB -15 10 5 0 Benzoflex354 -5 10 15 20 Results _________________ _______________ _______________ __________ Transfer -4/5 4/5 4/5 4/5 Flexibility -4/5 4 3 2 Film Forming -3 4 4/5 4 Migration on 3/4 3 paper _____ ________ ________ ________ 40°CWash 5 5 5 5 60°CWash 4/5 4 4 3/4

-EXAMPLE EXAMPLE EXAMPLE EXAMPLE EXAMPLE

______________ 43 44 45 46 47 Base(ii) 80 80 80 80 80 EastmanTXlB 15 10 5 0 20 DINA 5 10 15 20 0 Results -______________ Transfer 4/5 4/5 4/5 4/5 4/5 Flexibility -3 2/3 2/3 3 2 _____ 4/5 3 2/3 2 Migration on paper -3 2 1/2 1 3 40°CWash -4 3 3 2/3 2 60°CWash -3 2 2 2 4 The samples which gave the best results for 40 °C wash were examples 31, 39 and 43.

All of these contain 5 % of the secondary plasticizer. It appears the optimum levels of secondary plasticizer is about 5 %, whatever plasticizer is used.

Table 4 shows formulae based on those in Table 3, but they now additionally contain pigment, in order to assess suitable viscosity and pigmentation levels.

Table 4

EXAMPLE EXAMPLE EXAMPLE

_____________ ________ 48 49 59 Eastman TXIB ____ 46.6 46.6 46.6 Dioplex 7017 _______ 5 -- Benzoflex 354 _______ -5 -DNA ___ --5 Pentrone A4D _________ 0.72 0.72 0.72 Cabosil MS ____ 1.048 1.048 1.048 Ti02 _______ ______ _______ _________ Griltex l682E _________ 18.152 18.152 18.152 -LP3202 _________ 28.48 28.48 28.48

EXAMPLE EXAMPLE EXAMPLE

_____________ _________ 51 52 53 Eastman TXIB _________ 34.95 34.95 34.95 Dioplex 7017 _______ 3.75 -- Benzoflex 354 _______ -3.75 -DNA _____ --3,75 Pentrone A4D ________ 0.54 0.54 0.54 Cabosil MS _____ 0.786 0.786 0.786 Ti02 ______ 25 -25 25 Griltex 1682E ________ 13.614 13.614 13.614 LP3202 ________ 21.36 21.36 21.36

EXAMPLE EXAMPLE EXAMPLE

____________ ________ 54 55 56 Eastman TXIB _________ 40.775 40.775 40.775 Dioplex 7017 _________ 4.375 ___________ ___________ Benzoflex 3j _____ _________ 4.375 ___________ DNA _____ _______ _____ 4.375 Pentrone A4D _________ 0.63 0.63 0.63 CabosilM5 _______ 0.917 0.917 0.917 Ti02 ________ 12.5 12.5 12.5 Griltex_1682E ________ 15.883 15.883 15.883 LP3202 _____-24.92 24.92 24.92 Out of the above formulae in Table 4, the ones that gave the most flexibility and most consistent resistance to 40 °C and 60 °C washing were those containing Benzoflex 354; it therefore appears to be a favourable secondary plasticizer and we can use it whilst optimising the level of Ti02 to give opacity while not impairing flexibility too much. The level of Cabosil also needs to be optimised to give the best rheology for printing.

Example 55, containing about 5 % Benzoflex 354 and 12.5 % white pigment gave good results for flexibility and wash resistance, while being fairly opaque. This appears to be roughly the level of Ti02 required.

Claims

Claims 1. A composition for transferring a printed image onto a substrate comprising one or more of an acrylic resin and isobutyrate plasticizer.
2. A composition comprising an acrylic resin and isobutyrate plasticizer.
3. The composition according to claim I or claim 2 comprising: a. 10-40 wt% acrylic resin, and b. 10-50 wt% isobutyratc plasticizer, based on the total weight of the composition.
4. The composition according to any previous claim comprising: Is a. 20-3 0 wt% acrylic resin, and b. 25-40 wt% isobutyrate plasticizer, based on the total weight of the composition.
5. The composition according to any previous claim wherein said composition comprises a hot melt resin.
6. The composition according to claim 5 wherein the hot melt resin is a polyether resin.
7. The composition according to claim 5 wherein the hot melt resin is a polyester resin.
8. The composition according to claim 5 wherein the hot melt resin comprises both a polyether and polyester resin.
9. The composition according to any one of claims 5 to 8 wherein the hot melt resin is present in an amount 1-25 wt% based on the total weight of the composition.
10. The composition according to claim 9 wherein the hot melt resin is present in an amount of 10-15 wt% based on the total weight of the composition.
11. The composition according to any previous claim wherein said composition comprises a white pigment.
12. The composition according to claim 11 wherein the white pigment is present in an amount 1-25 wt% based on the total weight of the composition. F
13. The composition according to claim 11 wherein the white pigment is present in an amount 10-15 wt% based on the total weight of the composition.
14. The composition of any one of claims 1 to 13 comprising a second plasticizer.
15. The composition according to claim 14 wherein the second plasticizer is F present in an amount of 1 to 25 wt%, preferably 2 to 10 wt% based on the total weight of the composition.
16. Use of a composition as defined in any one of claims 1 to 15 as a transfer adhesive in a transfer printing process.
17. A method of producing a printed sheet comprising: a. printing a coloured ink on to a carrier substrate, and b. applying a composition as defined in any one of claims 1 to 15 to the printed ink.
18. The method according to claim 17 wherein the coloured ink is applied by lithographic printing.
19. The method according to claim 17 or claim 18 wherein the ink is heat set before the composition is applied.
20. The method according to any one of claims 17 to 19 wherein the composition is applied by screen printing.
21. The method according to any one of claims 17 to 20 wherein the composition is heat set.
22. The method according to any one of claims 17 to 21 wherein the carrier substrate is paper.
23. A printed sheet obtainable by the method of any one of claims 17 to 22. F
24. A method of transfer printing comprising: a. placing the printed sheet as defined in claim 23 on a second substrate such that said composition is in contact with the second substrate, and b. applying heat and/or pressure to the printed sheet in order to transfer the composition and ink from the carrier substrate to the second substrate.
25. The method according to claim 24 wherein the second substrate is a textile.
26. A substrate having an image printed thereon, wherein the image is printed by the method as defined in claim 24 or 25.