ITVA20090014A1 - GLUING FILM ON A SUBSTRATE FOR THE NOBILIZATION OF SURFACES EXPOSED TO THE EXTERNAL ENVIRONMENT - Google Patents

Description

BACKGROUND

TECHNICAL FIELD

The present invention generally relates to the finishing of surfaces by gluing a pre-constituted polyvinyl chloride (PVC) based film on the substrate surfaces, capable of resisting atmospheric agents and sunlight.

DISCUSSION OF KNOWN ART

The ennobling of visible surfaces of artifacts produced with materials often substitutes for natural materials and suitable for reducing the production costs of such objects and / or giving them technical and long-lasting properties of particular value, is a practice widely used industrially. The prefabricated film is commonly glued on the visible surfaces of the product using polyurethane or polyester "hot melt" glues.

The characteristics of the prefabricated film based on polyvinyl chloride (briefly PVC) must be such as to allow the film to adhere to surfaces that may also have curved parts and / or stairways and must therefore have adequate plasticity.

For artifacts intended to be exposed to atmospheric agents and in particular to sunlight, such as for example in the case of frames and fixtures such as windows and external doors, the absorption and resistance to UV radiation is a requirement of primary importance, therefore the PVC-based film, in addition to plasticizing components and pigments often contains stabilizers, anti-oxidants and materials capable of absorbing UV radiation. The solid color pigmented films or printed or treated in such a way as to give them an appearance similar to that of a paint or to the surface of precious materials such as wood of particular essences, are commonly associated by hot lamination or coextruded with a thin external surface film of marked hardness and scratch resistance, commonly based on PMMA (polymethylmethacrylate) or PET (polyethylene terephthalate), which can commonly be transparent and possibly have the external surface embossed or in any case "textured" to give even more pleasant tactile and visual surface characteristics to the artifact.

There is a large technical literature on the different formulations of mixtures based on polychloride of vinyl and laminated surface films together to form a preformed glue-able surface finishing film, as well as numerous techniques and procedures for the creation of tactile and visual effects such as the creation of random fibrous patterns that reproduce in the texture, color and tonality, the appearance of wood of particular essences.

Publications JP 8157676 (A) discloses a PVC film for finishing curved surfaces based on a mixture of PVC, two different types of acrylic resins of different molecular weight and a plasticizer.

Document CA 2502341 (A) describes a coextrusion process to coat a product with a PVC-based natural wood-like film with pigments of at least two different colors applied separately on the surface of the product, controlling the delivery of the two differently pigmented mixtures.

EP 0587353-A1, discloses the manufacture of a decorative laminate sheet having the feel of a coating. The ennobling film consists of a PVC sheet on which a hard coating layer is formed consisting of a material that can be cured with UV light and its manufacturing process.

The use of PVC-based ennobling films containing, according to current practice, monomeric or polymeric plasticizers has been found unsatisfactory in many cases, especially for products which undergo significant exposure of the surface ennobled by the film to solar radiation (UV). After a long period of exposure which in the best cases can be several years, detachment of the film from the substrate with the formation of bubbles and other phenomena attributable to a loss of local adhesion between the ennobling film and the underlying surface are observed. of the product be it extruded PVC, metal sheet, plywood, chipboard and the like.

DESCRIPTION OF THE INVENTION

After in-depth studies of the possible mechanisms of loss of adhesion of the PVC-based ennobling film glued to the surface of a product with "hot melt" glues, it has been demonstrated and it has long been generally accepted that the failure mechanism due to loss of adhesion is due to the migration over time of the plasticizer until it reaches the interphase and the glue, a fact that, especially in conditions of high humidity, causes detachment of the film from the surface of the product.

By testing numerous hypotheses through accelerated aging test campaigns, the applicant found that by using a mixture of polyvinyl chloride (PVC) and polyacrylate-grafted vinyl polychloride (PVC_graffato), it is possible to obtain a perfectly laminable PVC-based blend. from which to obtain an ennobling film with adequate plasticity characteristics, practically free of monomeric and / or polymeric plasticizing compounds capable of migrating towards the adhesion interphase with the result of eliminating the onset of detachments.

The weight ratio between the polyvinyl chloride and the polyacrylate in the component part of polyacrylate grafted vinyl chloride (briefly PVC_cratched) can vary. Within a variation of the percentage ratio between 40 and 60, there were no significant deviations in the trend of the mechanical characteristics obtainable from mixtures of the same with non-grafted PVC. To conduct comparative tests it was therefore decided to use a PVC grafted at 50% by weight with polyacrylate.

Optionally, the basic mixture of PVC and scratched PVC can also contain a copolymer of vinyl chloride and one or more materials belonging to the group composed of ethylene-vinyl acetate-carbon monoxide, ethylene-butylacrylate-carbon monoxide, ethylene-nbutylacrylate glycidyl methacrylate, ethylene -ethyl acrylate, ethylene methyl acrylate, ethylene ethyl acrylate, ethylene butyl acrylate and ketone ethylene ester.

The weight ratio between the component part of non-grafted PVC and the component part of grafted PVC and optional amount of vinyl chloride copolymer and the materials indicated above, of the base mixture can vary within a wide range depending on the type of application, in consideration of the fact that a higher content of grafted PVC determines greater plasticity.

Generally, the non-grafted PVC (for example of the K57 and / or K60 type) can be present in a variable weight percentage from a maximum of about 80% up to a residual value of almost 0%, the stapled PVC and the content in copolymer if present, constituting the rest of the base mixture.

The mixture can be stabilized by adding organic compounds of Sn and / or metal soaps, for example based on Ca / Zn salts. Preferably, a small amount of an epoxidized vegetable oil, such as epoxidized soybean oil, can also be added up to a maximum amount of about 8 phr (parts per 100 of resin).

To increase the ability to resist solar radiation over time, small quantities of UV absorbing substances and small quantities of antioxidants up to a maximum content of about 3 phr can be added to the PVC mixture, as well as internal and external lubricants. , as commonly used for the production of rigid PVC film by calendering and / or by extrusion.

Hue and coloring of the ennobling film are commonly achieved by adding organic and inorganic pigments to the mixture in quantities up to about 30 phr.

Furthermore, mineral fillers such as calcium carbonate and / or talc and the like can also be added to the mixture, up to a quantity of about 20 phr.

The film obtained by calendering and / or extrusion of the PVC-based mixture can have a thickness between about 80 and about 300 µm, depending on the application contemplated.

The precise formulation of the mixture with which the ennobling film is made obviously depends on the intended application and therefore on the mechanical characteristics of rigidity, elongation, etc. required by the particular application which may include a flat rolling operation or rolling by winding etc. on the support surface after interposition of the glue.

To obtain specific effects such as the effect of imitation wood or decorative prints, the PVC-based film, after printing or other surface treatment, can be laminated over the external surface of the PVC base film (decorated or not. decorated) to a transparent or opaque film of relatively harder material than PVC film, such as for example a PMMA, PVF or PET, whose thickness can generally be between about 10 and 200 µm, according to common practice, or painted with lightfast varnishes, with an effect, in both cases, smooth or structured / embossed (textured).

EXAMPLE 1

From laminated films of different mixtures of PVC with molecular weight K57 and PVC grafted at about 50% by weight with polyacrylate, in various weight ratios between the two parts, and having a thickness of 130 µm, numerous strips or specimens of 15 mm wide for a section of about 1.95 mm <2>, oriented transversely and longitudinally with respect to the direction of lamination of the different films.

The specimens were subjected to tensile strength tests and the results for the transverse specimens are shown in Table 1, while the results for the longitudinal specimens of the films of different compositions are shown in Table 2.

TABLE 1

Sample PVC PVC Load Transversal elongation (K57) stapled total applied with

polyacrylate

Not %

1 60 40 49 187

2 50 50 47 191

3 40 60 37 211

4 30 70 31 216

5 20 80 30 221

6 10 90 25 231

7 0 100 21 245

TABLE 2

Sample PVC PVC Load Longitudinal elongation (K57) stapled total applied with

polyacrylate

Not %

1 60 40 61 179

2 50 50 54 1800

3 40 60 46 186

4 30 70 39 193

5 20 80 32 201

6 10 90 25 209

7 0 100 17 216

The results show the marked effect on the plasticity characteristics of the

content of grafted PVC in the mixture, the "limit sample", consisting of

only grafted PVC reaches values of mechanical characteristics

comparable to those of plasticized films with plasticizer content between

25 and 30 phr, and can also be suitable for special applications that

require very high plasticity.

EXAMPLE 2

From laminated films of mixtures of PVC with molecular weight K57 and of PVC grafted with 50% of polyacrylate and having a thickness of 250 µm, numerous strips or specimens of 15 mm in width for a section of about 3.75 mm were obtained. 2>, oriented transversely and longitudinally with respect to the lamination direction of the different films.

The specimens were subjected to tensile strength tests and the results for the transverse specimens are shown in the following Table 3, while the results for the longitudinal specimens of the films of different compositions are shown in Table 4.

TABLE 3

Sample PVC PVC Load Transversal elongation (K57) stapled total applied with

polyacrylate

Not %

1 70 30 122.19 154.43

2 70 30 123.12 158.02

3 60 40 93.15 225.44

4 60 40 88.34 200.08

5 60 40 88.63 213.33

6 50 50 83.31 218.60

7 40 60 74.98 222.97

8 30 70 64.48 230.55

9 20 80 57.14 235.86

10 10 90 53.71 240.10

11 0 100 48.34 242.98

TABLE 4

Sample PVC PVC Load Longitudinal elongation (K57) stapled total applied with

polyacrylate

Not %

1 70 30 136.3 179.0

2 70 30 131.5 149.4

3 60 40 97.6 197.4

4 60 40 101.2 207.8

5 60 40 102.8 212.3

6 50 50 84.7 226.7

7 40 60 75.0 239.2

8 30 70 65.2 251.7

9 20 80 55.5 264.2

10 10 90 45.8 276.7

11 0 100 18.0 300.0

The results show the marked effect on the plasticity characteristics of the grafted PVC content in the mixture, the sample consisting of grafted PVC only (i.e. with virtually no non-grafted PVC content) reaches mechanical characteristics values comparable to those of plasticized films with plasticizer content between 25 and 30 phr.

The data for a 250 µm film confirm the characteristics already obtained for the 130 µm film. Moreover, the material can be easily calendered at both 130 and 250 µm.

EXAMPLE 3

Films of different formulations have been tested, both in terms of several and different resins used together with the polyacrylate to pre-constitute the part of grafted PVC to be mixed subsequently with the non-grafted PVC to form the PVC / grafted PVC mixture or added to a base mix. PVC / PVC stapled already formed.

A first campaign of tests carried out by adding to the basic mixtures of PVC and PVC grafted with polyacrylate, quantities of vinyl chloride copolymer with one or more of the materials belonging to the group composed of ethylene-vinyl acetate-carbon monoxide, ethylene-nbutyl acrylate- carbon monoxide, ethylene-nbutylacrylate glycidyl-methacrylate, ethylene-ethyl acrylate, ethylene ethyl acrylate, ethylene methyl-acrylate, ethylene ethyl acrylate, ethylene butyl acrylate, ketone ethylene ester, produced results that demonstrate a clear corrective effect on the mechanical and tactile characteristics of ennobling films obtained by calendering the mixture, which can be carried out either by adding one or more of the aforementioned copolymers to a pre-constituted mixture of PVC / PVC grafted with polyacrylate, or by adding the copolymer in partial replacement of the polyacrylate in forming the part of PVC grafted by then mix with the non-grafted PVC.

The presence of polyacrylate for a significant percentage, generally not less than 10% by weight, in the grafted PVC part appears preferable, as the polyacrylate exhibits a particularly marked plasticizing effect when compared with that produced by copolymers of vinyl chloride and the materials of the above group defined.

By way of example, data obtained with PVC / PVC blends grafted with polyacrylate and with the addition of ethylene-vinyl acetate-carbon monoxide copolymer are shown in the following Table 5.

TABLE 5

Sample PVC PVC Copolymer Loaded Transversal elongation (K57) grafted of CV and applied total with

EVaCO polyacrylate

Not %

1 70 30 5 86 145

2 70 30 10 58 185

3 30 70 5 39 170

4 30 70 10 33 200

The results show the corrective effect on the plasticity (elongation) characteristics that can be achieved by adding, in the example shown, a copolymer of CV and EVaCO to the different pre-made mixtures of PVC / PVC stapled with polyacrylate and obtaining a more pleasant tactility of the film. Similar or different corrective effects are exhibited by additions of other of the copolymers indicated above.

Claims (12)

CLAIMS 1. Ennobling film to be glued on external flat, curved and / or stairway surfaces, of fixtures and frames, consisting of a mixture of polychloride of vinyl and polychloride of vinyl stapled to polyacrylate. 2. An enhancement film according to claim 1, wherein the polyvinyl chloride and the polyacrylate in said part of the polyacrylate grafted vinyl chloride are present in a percentage ratio of between 40 and 60. 3. Ennobling film according to claim 1, wherein the non-grafted PVC is present in the mixture in a percentage by weight comprised between a maximum of 80% and a residual value of about 0%. 4. Ennobling film according to claim 1, further comprising a minority part of vinyl chloride copolymer with one or more materials belonging to the group consisting of ethylene-vinyl acetate-carbon monoxide, ethylene-nbutyl acrylate-carbon monoxide, ethylene- nbutylacrylate glycidyl-methacrylate, ethylene-ethyl-acrylate, ethylene-methyl-acrylate, ethylene-butyl-acrylate and ketone-ethylene-ester. 5. Ennobling film according to claim 4, wherein said copolymers are present in an overall quantity from 0 to 30 phr. 6. Ennobling film according to claim 1, wherein at least one stabilizer belonging to the group consisting of organic compounds of Sn, soaps of Ca or Zn salts is added to the mixture. 7. Enhancing film according to claim 1, wherein an epoxidized vegetable oil is added to the mixture as a co-stabilizer. 8. Ennobling film according to claim 1, further containing UV light absorbing and antioxidant substances in quantities up to 3phr. 9. Enhancing film according to claim 1, further comprising pigments and / or mineral fillers in an amount up to 20 phr. 10. Ennobling film according to claim 1, further comprising a transparent or opaque film of a material belonging to the group composed of PMMA, PVF and PET, laminated over the outer surface of the polychloride-based ennobling film, or a film of acrylic paint. The enhancement film according to claim 5, wherein said film laminated on the outer surface of the PVC-based film has a smooth, textured or embossed surface. 12. Ennobling film according to claim 1, wherein said vinyl polychloride has a molecular weight comprised between K57 and K60.