DK146476B - PROCEDURE FOR MANUFACTURING A VARIOUS EXPANDED SHEET MATERIAL - Google Patents

Description

in 148476

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a process for preparing a different expanded sheet material wherein selected regions of a sheet of an expandable thermoplastic material containing a blowing agent are coated with a printing ink containing a blowing agent accelerator and the sheet is heated to a temperature. , by which the blowing agent in contact with the accelerator decomposes so that the selected areas expand to a greater extent than the other areas of the sheet. The sheet materials thus produced can be used, for example, as wall coverings, floor coverings, decorative laminates and transfer pictures.

The manufacture of sheet materials having relief effect upon various expansion of a thermoplastic sheet material provides the important advantage of eliminating the use of embossing rolls in the manufacturing process. Thus, while the effect of an embossing roller is to physically change the surface character of the sheet material, a similar appearance can be achieved by chemical means if selected areas of the sheet material are expanded to varying degrees.

Expansion of a thermoplastic sheet material can be accomplished by incorporating a blowing agent into the sheet and heating the sheet to a temperature at which the blowing agent disintegrates. The blowing agent is suitably dispersed in the thermoplastic material prior to forming the sheet thereby ensuring a complete distribution of the blowing agent in the sheet. Various expansion of the thermoplastic sheet material can be achieved by a "kicker". Accelerators are well known and their effect is to lower the decomposition temperature of certain blowing agents. If a foreign carrier is only associated with the blowing agent in certain areas of the sheet, only a reduction of the disintegrating temperature of the blowing agent is obtained in those areas. As a result, a higher degree of expansion is achieved in the sheet areas containing accelerates than in those regions which do not contain accelerators when the sheet is heated to a given temperature for a suitable period of time.

Various expansion of an expandable thermoplastic sheet material containing a blowing agent can be achieved by applying only an accelerator to certain areas of the sheet surface before heating the sheet to provide expansion. The application of an accelerator to the surface of the sheet has attractive advantages as the sheet containing the blowing agent can be formed in one operation and since the necessity of incorporating an accelerator into selected portions of the sheet forming mixture is eliminated. In addition, the use of complicated printing techniques including applying selected inks to the areas of the sheet containing the accelerator is avoided and, if desired, the accelerator can be applied together with the ink. In reality, the difficulty of keeping a record is to apply separately to the accelerator and the ink on the sheet so that in most cases it is preferred to apply them together.

The preparation of a different expanded sheet material in the manner indicated in the introduction is known, for example, from NO Patent No. 125,966. Thus, the sheet material prepared according to this patent contains in the manner described above a blowing agent and when the sheet is heated to the temperature at which the blowing agent decomposes, it expands. Using an accelerator achieves expansion only in selected areas. An accelerator is a component that lowers the decomposition temperature of the blowing agent. Thus, when heating an expandable sheet which has been applied to a accelerator in certain areas, expansion will preferably occur in the regions where the accelerator has been applied. However, the method of NO patent no.

125,966 not satisfactorily. Thus, insufficient ink color adhesion is encountered during the preparation of a sheet material, which results in the ink being prone to being removed as the sheet of the applied ink undergoes various processing steps which, in commercial fabrication, precede the step of heating the sheet to produce swelling. Such processing steps include the various printing steps, rolling the printed sheet onto a roll, as well as the simple passage of the sheet over rollers. Removal of ink has the effect of limiting the expansion in the areas where the ink has been removed and an aesthetically unappealing product is obtained which cannot be used.

There is also the possibility that ink that has been peeled off by a roller could be returned to the sheet in an undesirable location. This will result in expansion in areas other than where it is desired.

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GB Patent No. 1,159,645 is known to apply a catalyst (i.e., an accelerator) to the entire surface of the expandable sheet material, after which a deactivator is applied to selected areas and the deactivator prevents the catalyst from carrying out its work. However, in this method, a composition containing both ink and accelerator cannot be used.

From GB Patent No. 1,268,828, it is known to apply a solvent to the surface of a resin layer to etch this surface, so that the surface of a synthetic resin article is rendered non-transparent, rough or porous by application of a solvent and a non-solvent. However, this method does not concern the production of expanded sheet material.

It is the object of the invention to provide a method of the kind known in the introduction, eliminating the aforementioned disadvantages of the method known from NO Patent No. 125,966.

This is achieved by a process which is characterized by coating the sheet with a lacquer containing an organic solvent for the thermoplastic material and allowing the lacquer to dry at least partially before applying the ink.

The surprising discovery upon which the present invention is based is that if the sheet is coated with a lacquer prior to the application of the ink containing the accelerator, a substantially improved ink adhesion is obtained by the method. The mechanism of ink adhesion to the sheet is believed to imply that the particles (or molecules) of the ink are joined to the surface of the thermoplastic layer, and it will be readily apparent that the ink must therefore have access to the surface. In such circumstances, one would consider that the very last thing one would want to do is introduce a barrier between the accelerator-containing ink and the surface of the thermoplastic sheet. Initially, it was thus thought that the introduction of a lacquer layer between the ink and the thermoplastic sheet would not promote the ink adhesion. However, it has been found that the opposite effect is obtained, namely that applying a lacquer prior to the application of ink to the surface of the thermoplastic sheet surprisingly allows a significantly improved ink adhesion during the treatment.

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Satisfactory expansion throughout the depth of the sheet depends on the accelerator's migration through the depth of the sheet. Application of a varnish prior to application of the accelerator could conceivably provide an additional physical barrier to the desired migration of the accelerator. However, it is a further and unexpected advantage of the method according to the invention that the improvement of the ink color adhesion can be achieved without any significant reduction in the quality of the relief effect.

It is believed that treating the surface of the sheet material with the selected solvent-containing varnish causes an etching of the surface thereby improving the adhesion of the ink to the sheet and the presence of the solvent facilitating the migration of the later applied accelerator into the depth of the thermoplastic sheet. The selected solvent-containing varnish can be applied over the entire surface of the sheet or only in the areas to be subsequently applied to the ink containing the accelerator.

The method of the invention is particularly suitable for making wall coatings since the thermoplastic sheet material can be formed as a sheet without support or as a coating on paper, a non-woven synthetic fibrous web, a spun adhesive fibrous web or other suitable base. Different expansion of the thermoplastic material results in the formation of a sheet with an attractive appearance which is suitable for decoration of walls or ceilings. However, the method of the invention is not limited to the manufacture of wall coverings and the sheet materials can also be used as floor coverings, decorative laminates, display labels and transfer images. In the manufacture of floor coverings, the thermoplastic sheet material is usually formed on a relatively solid basis which may be a suitable plastic material, a felted sheet material or a woven or knitted fabric, for example made from natural or synthetic fibers.

The thermoplastic sheet can be formed from any suitable expandable synthetic resin material. Preferred materials include polymers of vinyl chloride or copolymers of vinyl chloride and another copolymerizable monomer such as vinyl acetate or an acrylic or methacrylic monomer such as an ester of acrylic or methacrylic acid or the acrylic acid itself or the methacrylic acid. The expandable sheet or layer may be formed from a plastisol, in which case the thermoplastic polymer or copolymer is admixed with a blowing agent, a controlled catalytic stabilizing agent on the blowing agent under the selected process conditions, a plasticizer which may be any of the the commonly used phthalate compounds and pigments or fillers. The piastisol is formed as a sheet or layer in any suitable manner and may be applied, for example, to a base of fibrous web or paper or similar material as mentioned above, the weight of the plastisol, for example, being from 40 to 800 g / m 2.

The precise choice of blowing agent will depend on the specially used thermoplastic material and the decomposition temperature in the presence of the accelerator should be adapted to the thermoplastic material. Blowing agents are well known and are described in the literature. Suitable blowing agents include azobis-formamide and azobisisobutyronitrile. The blowing agent may conveniently be present in the thermoplastic sheet in amounts of up to 15% by weight, eg 1-15% by weight, preferably from 3 to 9% by weight, based on the weight of the expandable synthetic resin material.

An alternative technique for use in the manufacture of the expandable thermoplastic layer is heat melt coating. This technique can be used with a wide range of materials such as with polyethylene, polyvinyl chloride, polyester and acrylic polymers.

The application of the solvent-containing varnish can be carried out in any suitable manner and satisfactory results are obtained if simply wetting the thermoplastic layer or sheet with the selected varnish. Since the solvent contained in the lacquer appears to be at least partially etching the sheet or the surface of the coating, the solvent should be selected according to the nature of the thermoplastic material. Therefore, in the case that the expandable thermoplastic layers or sheets are based on polymers of vinyl chloride or copolymers of vinyl chloride and other copolymerizable monomers, it is preferred that the organic solvent be polar since such solvents usually have a greater affinity for the thermoplastic material than non-polar solvents. .

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Suitable solvents which may be included in the lacquer applied to the thermoplastic sheet include hydroxyl compounds such as, for example, mono- and polyhydric alcohols, aliphatic and al-cyclic ethers such as tetrahydrofuran, esters such as ethyl acetate or isopropyl acetate, glycol esters such as glycol esters, glycol esters, ethyl acetate, aliphatic and alicyclic ketones such as methyl ethyl ketone, methyl isobutyl ketone or cyclohexanone, halogenated hydrocarbons, especially chlorinated aliphatic hydrocarbons, nitro compounds such as nitropropane or nitrobenzene, and Lewis bases such as substituted amide and dimethyl amide, e.g. ) sulfoxides such as dimethyl sulfoxides.

There may be benefits associated with using strongly. polar solvents in some cases, and in such cases .... it may be desirable to use the selected solvent. in connection with a less polar or non-polar solvent. The latter material serves as a diluent; for the polar solvent and may conveniently be a hydrocarbon such as toluene, xylene or denatured (methylated) spirit.

In the special case where thermoplastic sheets of vinyl chloride homopolymers and copolymers are formed, it has been found that aliphatic ketones such as methyl ethyl ketone and aromatic hydrocarbons such as toluene or xylene are advantageous to use as solvents.

The rate of application of the solvent contained in the lacquer> on the expandable thermoplastic sheet material will depend on the application method used. As a rule, an application rate based on the amount of solvent contained in the lacquer will be 2 2. of from 10 to 700 g / m, preferably 30 to 500 g / m, give satisfactory results. In the special case where the varnish is applied at gravity, the rate of application of the solvent 2 can be from 25 to 300 g / m, preferably from 50 to 150 g / m.

As mentioned, the selected solvent is applied as the solvent phase in a varnish. The use of a lacquer provides a convenient opportunity to treat the surface of the thermoplastic material with an additional component such as a frosting or pigment. The heat treatment in the expansion step can produce a glossy surface on the resulting sheet material and it may be desirable to introduce a matting agent to reduce this effect. As a binder, the lacquer may contain any suitable resin such as a polymer or a copolymer of ethylenically unsaturated monomers, e.g., vinyl and / or acrylic or methacrylic monomers. Other suitable binders for the varnish include polyurethanes, polyesters and epoxy resins. The lacquer can be applied by any well-known technique such as gravure, roll coating, silkscreen or flexographic printing and since these methods can also be used to apply the blend containing an accelerator, the whole technique is well suited for a single row industrial operation.

It is particularly preferred to use deep pressure rollers for the application of a layer to the surface of the thermoplastic sheet material. The gravure rollers will preferably be engraved with 30-80 lines per minute. cm.

The accelerator mixture may include the selected accelerator in a solution or suspension in ink. Thus, the mixture will typically include the accelerator mixed with a pigment, a binder and a dispersed phase. The accelerator will usually be a compound of zinc, cadmium or lead and the accelerator will conveniently be a salt of zinc, cadmium or lead, although other compounds of the selected metals such as zinc oxide may also be used. Zinc, cadmium or lead salts may be formed of inorganic or organic acids. Inorganic acids which can be used for salt formation include hydrochloric and nitric acids, while suitable organic acids include carbonic, oxalic, acetic, lactic, citric, formic, sebacic, octanoic, stearic, phthalic and benzoic. The ink mixture may conveniently contain up to 25 wickets of the accelerator, preferably from 5-20% by weight. An accelerator that is appropriate to use is zinc octoate.

The solvent for the ink can be any of the commonly used inks for ink used in the manufacture of printed wall coatings. Thus, for example, ketones such as methyl ethyl ketone, esters such as 2-ethoxyethyl ethyl acetate, nitro compound such as nitropropane and hydrocarbons such as toluene can all be used advantageously. The pigment content of the ink will vary according to the particular pigment chosen, but effective results will usually be obtained with ink mixtures containing up to 20% by weight, preferably 5-15% by weight pigment.

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The formulation of the accelerator mixture will depend on the particular way in which the ink is to be printed on the treated sheet material. However, the accelerator blend may be applied with equal advantage in printing using any conventional technique such as those mentioned above for the application of the varnish.

As mentioned above, the expandable thermoplastic sheet material is preferably formed from a plastisol and, in such cases, the degree of gelation of the expandable sheet material at the time the varnish and accelerator is applied is important.

Thus, if the degree of gelling is too low, the surface character of the layer will be destroyed during the application of the varnish, especially if such application involves passage of the sheet through the clamping slot of the pressure rollers. If the reverse gelation rate is too high, it will be difficult to achieve satisfactory expansion of the sheet. Satisfactory gelation of the sheet material can be obtained by heating it to 110-140 ° C for a relatively short period of time. A few minutes of heating at low temperatures is usually sufficient, while heating for less than one minute may be appropriate at higher temperatures.

Expansion of the printed thermoplastic sheet material eel can take place in a line-up operation. printing steps. Alternatively, the printed sheets can be stacked as sheets or rolled onto a roll and expanded later. In this latter case, there may be a tendency for the accelerator to move - from one sheet into the adjacent stacked or rolled sheets, resulting in undesirable expansion in areas of these adjacent sheets.

The thermoplastic sheet material can be provided with a coating which is impermeable to the accelerator after the printing step to avoid this problem and the impermeable layer can be applied either to the back or front of the sheet before stacking or coiling. The layer is preferably applied as a transparent lacquer on the front of the printed sheet after the last printing. step. Application of the impermeable layer to the front is preferred because such coating provides barrier to acceleration of the accelerator and may further serve as a wear layer to protect sheet material during use. In addition, applying a lacquer 1Λ 647 6 9 in a final step after printing may provide a convenient opportunity to introduce an additional agent onto the surface of the sheet, such as a matting agent.

If desired, the sheet material obtained by the method of the invention may be provided with an adhesive coating on the side to be applied to a substrate. In the special case where wall coverings are made, for example, the side of the sheet material to be applied to the wall or ceiling may be provided with a coating of a water activatable adhesive. The sticky coating can be provided at any convenient location during the preparation of the sheet material.

In the case of water activatable adhesives, the coating may be applied in the form of an aqueous solution, dispersion or emulsion on the surface of the sheet material and then dried. The adhesive may be applied in an amount of 2-30 g / m to the surface area and the adhesive may be a natural or synthetic resin material, a vegetable gum, a soluble starch or starch ether or other suitable material.

It may be advantageous to incorporate other ingredients into the adhesive coating, such as surfactants to improve the water-absorbing properties of the adhesive coating and fungicides to inhibit mold growth.

The process of the invention can be used to produce sheet materials with the most varying effects. Thus, for example, two or more applications of an accelerator blend may be performed on different areas of the sheet surface after the treatment with a solvent-containing varnish. Different pigments may be used in the different accelerator mixtures which may additionally contain different concentrations of the accelerator. After the expansion of such a sheet, a product is formed in which a variation of the degree of expansion is obtained which gives a product with a pleasant decorative effect.

For a better understanding of the invention, the preparation of a sheet material according to a preferred embodiment of the method according to the invention is described with reference to the drawing, in which fig. 1 shows a method for making a line of a sheet material according to the invention, in FIG. 2 is an enlarged fragmentary longitudinal section of an expandable thermoplastic sheet; FIG. 3 is a longitudinal sectional view of FIG. 2 showing a lacquer coating; FIG. 4 is a longitudinal sectional view of FIG. 3 after applying an ink to the treated surface, and FIG. 5 is a longitudinal sectional view of FIG. 4 sheet material after expansion.

It will be understood that FIG. 1-5 are schematic only and no attempt has been made to show the relative thicknesses of the different layers that make up the sheet material.

One. expandable thermoplastic layer 1 is applied as a plastisol to a sheet of suitable paper 2 and is partially gelled by the furnace 12 to produce a sheet material as shown in FIG. 2. The sheet material thus formed is fed to the clamping gap between a pair of rollers 6 as shown in FIG. 1 and receives a coating of a varnish 3 from a bath 7, after which it is partially dried by an oven 11 to produce a lacquered sheet as shown in FIG. 3. The lacquer contains a dispersion of a matting agent in a solution of. a vinyl chloride homo or copolymer in an organic solvent with affinity to the thermoplastic sheet. Suitable varnishes are described in more detail in Examples 1 and 2 below.

The lacquered sheet is then fed to the clamping slot between a pair of conventional printing rollers 8 and printing ink from a bath 9 is applied. only certain areas of the lacquered surface of the sheet. The ink contains a pigment and one. forceps suitable for the inflatable. agent present in the thermoplastic layer 1 and formulations of such inks are described in more detail in Examples 1 and 2 below. The sheet material now has an appearance as shown in FIG. 4 and has a plurality of spaced regions 4 coated with accelerator-containing ink.

The printed sheet shown in FIG. 4 then comes to a furnace 10 where the sheet achieves a temperature which lies between the decomposition temperature of the blowing agent and the mixture of the blowing agent and the accelerator. Thereby different expansion is obtained to form a product as shown in FIG. 5, in which the parts of the sheet which have received an application of accelerator-containing ink are expanded to a greater extent than those parts of the sheet which have not received such coating. The resulting sheet material has an attractive appearance and can be used as a wall covering.

The process according to the invention is illustrated in the following by means of some examples. In the examples, parts denote parts by weight.

Example 1 a) Preparation of expandable thermoplastic sheet A mixture consisting of

Polyvinyl chloride 100 parts

Dicapryl phthalate (plasticizer) 65 parts

Organo-tin stabilizer 1 part

Epoxidized oil stabilizer 6 parts

Azobisformamide 6 parts

Titanium dioxide 40 parts

Mine. turpentine 5 parts were applied by means of a scraper to a thickness of 0.2 mm and a Λp dry weight of 190 g / m on a 90 g / m paper. The coating was gelled at a temperature of 120-130 ° C for 60 seconds to obtain an expandable thermoplastic sheet.

b) Treating the expandable sheet with solvent-based varnish

A varnish was prepared by dispersing the following recipe:

Vinyl chloride / vinyl acetate copolymer 18 parts

Silica matting agent 8 parts

Methyl ethyl ketone 40 parts

Xylene 10 parts

Toluene 24 parts 146476 12

The viscosity of the lacquer was adjusted by adding methyl ethyl ketone to 30 seconds (measured with Ford Cup # 4) and the lacquer was then applied to the surface of the gelled polyvinyl chloride layer prepared under a) using gravure roll engraved at 55 lines per minute. cm. After partial drying, the treated sheet was applied to the following ink mixture:

Vinyl Chloride Polymer in Methyl Ethyl Ketone 24 Parts 2-Ethoxy Ethyl Acetate 2.5 Parts

Toluene 13 parts

Zihkoktoat 24 parts

Pigment 7 parts

If necessary, the viscosity of the ink was adjusted to 30 seconds (measured with Ford Cup # 4) by the addition of methyl ethyl ketone. The ink was applied in a selected pattern using a gravure roller engraved with 47 lines per minute. cm and inflated at 200 ° C for one minute after a twenty hour interval.

The product obtained had an expansion in the printed areas of greater than 0.047 mm from the unprinted areas and an appropriate degree of maturity which in combination gave the material an attractive appearance. In addition, the product showed good ink adhesion.

Example 2

A varnish was prepared by dispersing the following recipe:

Polyvinyl chloride 18 parts

Silica matting agent 15 parts

Titanium dioxide 36 parts

Methyl ethyl ketone 23 parts

Toluene 8 parts

The viscosity of the lacquer was adjusted by adding methyl ethyl ketone to 30 seconds (measured with Ford Cup # 4) and the lacquer was then applied to the surface of a thermoplastic sheet made as described in Example 1 a). The application was carried out using 13 14 6 A 7 6 of a gravure roller engraved with 40 lines per. cm, after which the treated sheet was applied to the following ink mixture:

Polyvinyl chloride 18 parts

Pigment 9 parts 2-Nitropropane 40 parts

Methyl ethyl ketone 8 parts

Toluene 24 parts

Zinc octoate 18 parts

If necessary, the viscosity of the ink was adjusted to 30 seconds (measured with Ford cup # 4) by the addition of methyl ethyl ketone. The ink was applied in a selected pattern using a gravure roller engraved at 59 lines per minute. cm and inflated at 200 ° C for one minute after a seven-day interval.

The product obtained had an expansion in the printed areas greater than 0.059 mm from the unprinted areas and a satisfactory degree of maturity. The material had an attractive appearance and the product's ink adhesion was good.

Examples 3-12

Sheet materials were prepared in these examples in a manner analogous to that described in Examples 1 and 2. Examples 3-12 illustrate the use of the invention when various expandable thermoplastic materials, lacquers and accelerators are used in the process of the invention.

a) Manufacture of expandable thermoplastic sheet materials A and B

The following mixtures were applied by means of a scraper p to a thickness of 0.13 mm and a dry weight of 180 g / m on a 90 g / m paper.

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Sheet A B

Polyvinyl chloride homopolymer 100

Vinyl chloride / vinyl acetate copolymer - 100

Dicaprylphthalate 65 65

Organo-tin stabilizer 1 1

Epoxidized Oil Stabilizer 6 6

Azobisformamide 6 6

Ti tan dioxide 40 40

Mine. turpentine 5 5

The coatings were gelled at 120 ° C for 60 seconds.

b) Treatment of sheet materials A and B with solvent-containing varnishes

The following varnishes were prepared to treat sheets A and B.

Lacquer No. 123456

Vinyl chloride / vinyl acetate copolymer 23 23 20 - 17 12

Acrylic Resin - - - 20 - 13

Silica Matter - 20 - 20 - 8

Colored pigment - - - 10 6

Titanium dioxide _____ 36

Methyl Ethyl Ketone - 115 100 80 85 107

Toluene - - 55 25 62 48

Cylclohexanone - 30 10 Ethyl acetate 138 - - - - -

Isopropyl Acetate 90 ----- 2-Ethoxy Ethyl Acetate - - - 8 - 13 2-Nitropropane -20 ----

Tetrahydrofuran ------ 146476 15

The lacquer was applied to the gelled sheets A and B using a gravure roller engraved with 59 lines per square meter. cm. After partial drying, the treated sheets were applied to the following ink mixtures:

Ink No. I II III IV

Vinyl Chlorine d / Vinyl Acetate Copolymer - · - 17 17

Acrylic Resin 13 13 - -

Lead octoate - - - 20

Cadmium octoate - 14 - -

Zinc octoate - - 17

Zihkbenzoat 20 --.-

Methyl ethyl ketone 46 50 64 68

Toluene 28 23 31 29 2-Ethoxyethyl ethyl acetate 8 8--

Pigment 13 13 10 10

All the inks were applied with a viscosity of 25 seconds (as measured with Ford Cup # 4), the viscosities being adjusted by the addition of methyl ethyl ketone if necessary. The inks were applied using a gravure roller engraved at 59 lines per square meter. cm and inflated at 200 ° C for one minute after a 24 hour interval.

The examples and properties of the expanded expanded sheet materials obtained are shown in the following table.

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Ex. Sheet Sheet Ink Color Contrast1 Ink No # No in mm adhesion 3 A 4 II 0.17 good 4 A 5 III 0.40 5 A 6 IV 0.30 6 A 1 IV 0.31 "7 A 3 III 0.47 "8 A 2 III 0.45 9 B 6 I 0.20 10 B 1 II 0.06 11 B 3 IV 0.18 12 B 2 IV 0.21 1) The contrast is a measure of the difference between the expansion of the the printed areas relative to the unprinted areas.

The products obtained by Examples 3, 5, 8, 9 and 12 were matte.