阅读说明：本技术 低温反应固化型粘合剂的耐湿热性和耐化学试剂腐蚀性的提高 (Improvement of resistance to moist heat and chemical agent corrosion of low-temperature reaction-curable adhesive ) 是由 王辉 朱学进 陈曦 郭寿成 于 2018-06-05 设计创作，主要内容包括：本发明涉及低温反应固化型粘合剂的耐湿热性和耐化学试剂腐蚀性的提高。具体地,本发明提供了一种提高粘合剂与金属基材之间的粘合强度的方法,包括步骤：(a)提供第一基材,所述的第一基材为金属基材,并且所述的金属基材的至少一个主表面上沉积有DLC涂层；和(b)将一粘合剂施涂于所述的DLC层上,从而形成“第一基材-DLC涂层-粘合剂层”的粘合结构。本发明还提供了含有相应粘合结构的产品。本发明方法可显著提高粘合剂(尤其是LTR粘合剂)与金属基材之间的粘合强度,进而提高耐湿热性和耐化学试剂腐蚀性。(the present invention relates to an improvement in resistance to moist heat and resistance to chemical agents of a low-temperature reaction-curable adhesive. Specifically, the present invention provides a method for improving the adhesive strength between an adhesive and a metal substrate, comprising the steps of: (a) providing a first substrate, wherein the first substrate is a metal substrate, and at least one main surface of the metal substrate is deposited with a DLC coating; and (b) applying an adhesive to said DLC layer, thereby forming an adhesive structure of "first substrate-DLC coating-adhesive layer". The invention also provides products containing corresponding adhesive structures. The method of the invention can obviously improve the bonding strength between the adhesive (especially LTR adhesive) and the metal substrate, thereby improving the resistance to moist heat and chemical reagent corrosion.)

1. A method of increasing the bond strength between an adhesive and a metal substrate comprising the steps of:

(a) providing a first substrate, wherein the first substrate is a metal substrate, and at least one main surface of the metal substrate is deposited with a DLC coating; and

(b) an adhesive was applied to the DLC layer, thereby forming an adhesive structure of "first substrate-DLC coating-adhesive layer".

2. The method of claim 1, wherein the method further comprises:

(c) And (3) bonding a second substrate to the other main surface of the adhesive layer to form a bonding structure of 'first substrate-DLC coating-adhesive layer-second substrate'.

3. The method of claim 1, wherein the bond strength is bond strength under hot and humid conditions; and/or

The adhesive strength is the adhesive strength under the condition of being corroded by a chemical agent.

4. The method of claim 3, wherein the humid heat conditions comprise a temperature of 50-90 ℃ and a relative humidity of 80-99%; preferably 60-85 deg.C and relative humidity of 85-95%.

5. The method of claim 1, wherein the method further comprises: prior to step (a), the major surface of the first substrate to be bonded is subjected to physical vapor deposition to deposit a DLC coating thereon.

6. The method as claimed in claim 1, wherein the DLC coating has a thickness of 0.5-20 microns, preferably 1-10 microns, more preferably 2-6 microns.

7. The method of claim 1, wherein the first substrate is selected from the group consisting of: stainless steel substrates, aluminum substrates, and alloy substrates.

8. The method of claim 2, wherein the major surface of the second substrate to which the adhesive layer is adhered is deposited with a DLC coating.

9. The method of claim 1, wherein the adhesive comprises a PU-based adhesive.

10. The method of claim 1, wherein the adhesive is a low temperature reactive adhesive (LTR adhesive).

11. The method of claim 1 wherein in step (b) a reactive film comprising an adhesive is adhered to said DLC layer, thereby applying said adhesive to said DLC layer.

12. The method of claim 3, wherein the chemical attack conditions comprise exposure to a chemical selected from the group consisting of: alkaline material, acidic material, salt, sebum, alcohol, ether, ester material or combination thereof.

13. the method of claim 12, wherein the chemical agent comprises an acidic solution, preferably wherein the acidic solution has a pH of 3.0-6.5, more preferably 4.0-5.5.

14. The method of claim 12, wherein the chemical agent comprises an alkaline solution, preferably wherein the alkaline solution has a pH of 7.5 to 10.5, more preferably 8.0 to 10.

15. An adhesive product, said product comprising:

(a) The first base material is a metal base material;

(b) A DLC coating on at least one major surface of the metal substrate;

(c) An adhesive layer adhered to the outer surface of the DLC coating (i.e. the other major surface facing away from the metal substrate); and

(d) optionally a second substrate bonded to the other major surface of said adhesive layer.

16. The adhesive product of claim 15, wherein the second substrate is selected from the group consisting of: metal substrates, and non-metal substrates.

17. The adhesive product of claim 15, wherein the second substrate is a metal substrate and the major surface of the second substrate facing the adhesive layer has a DLC coating deposited thereon.

18. The bonded product of claim 15, wherein the bond strength S1 between the first substrate and the adhesive layer is 15N/mm or more after storage for 3 days under humid heat²(e.g., 15-25N/mm)²) Preferably not less than 18N/mm²More preferably not less than 20N/mm²。

19. The adhesive product of claim 15, wherein the adhesive product comprises an electronic product, a household product, a vehicle, or a ship.

20. Adhesive product according to claim 15, characterized in that the DLC coating has a thickness of 0.5-20 microns, preferably 1-10 microns, more preferably 2-6 microns.

Technical Field

The present invention relates to the field of adhesives, and more particularly to improvements in resistance to moist heat and resistance to chemical agents in low temperature reaction curable adhesives.

Background

Adhesive films, especially reactive adhesive films (or reactive adhesive films), can provide some adhesive strength on the surface of the substrate to be bonded. When the substrate to be bonded is a non-metallic substrate such as plastic, the adhesive film can generally provide better bonding strength.

When the substrate to be bonded is a metal substrate, the Low Temperature Reactive (LTR) film can be well bonded to a metal surface (e.g., Al, stainless steel plate) under appropriate curing conditions (e.g., 80-120 ℃ for 30-240 seconds). However, under normal, reliable storage conditions (e.g., 65 ℃, 95% relative humidity or 85 ℃, 95% relative humidity, 3 days), the bond is not stable. Such storage at high temperature and humidity results in a substantial reduction in the adhesive force between the adhesive and the metal, which in some practical applications results in adhesive failure, especially those involving bending/restoring forces of the adhesive substrate. This phenomenon has narrowed the application range of LTR films in the electronics market, since stainless steel is a common substrate in many applications.

In view of the above, there is an urgent need in the art to develop a new method capable of significantly improving the adhesion performance of an LTR film under high temperature and high humidity conditions.

disclosure of Invention

The purpose of the present invention is to provide a method capable of significantly improving the adhesion performance of an LTR film under high temperature and high humidity conditions.

In a first aspect of the present invention, there is provided a method of improving the bond strength between an adhesive and a metal substrate, comprising the steps of:

(a) Providing a first substrate, wherein the first substrate is a metal substrate, and at least one main surface of the metal substrate is deposited with a DLC coating; and

(b) An adhesive was applied to the DLC layer, thereby forming an adhesive structure of "first substrate-DLC coating-adhesive layer".

In another preferred example, the method further comprises:

(c) And (3) bonding a second substrate to the other main surface of the adhesive layer to form a bonding structure of 'first substrate-DLC coating-adhesive layer-second substrate'.

In another preferred embodiment, the adhesive strength is an adhesive strength under a wet heat condition; and/or

The adhesive strength is the adhesive strength under the condition of being corroded by a chemical agent.

In another preferred embodiment, the humid heat condition comprises a temperature of 50-90 ℃ and a relative humidity of 80-99%; preferably 60-85 deg.C and relative humidity of 85-95%.

In another preferred embodiment, the method further includes: prior to step (a), the major surface of the first substrate to be bonded is subjected to physical vapor deposition to deposit a DLC coating thereon.

In another preferred embodiment, the DLC coating has a thickness of 0.5 to 20 microns, preferably 1 to 10 microns, more preferably 2 to 6 microns.

in another preferred embodiment, the first substrate is selected from the group consisting of: stainless steel substrates, aluminum substrates, and alloy substrates.

In another preferred embodiment, the second substrate has a DLC coating deposited on the major surface thereof to which the adhesive layer is adhered.

In another preferred embodiment, the adhesive comprises a PU-based adhesive.

In another preferred embodiment, the adhesive is a low temperature reactive adhesive (LTR adhesive).

In another preferred embodiment, in step (b), a reactive film containing an adhesive is bonded to the DLC layer, thereby applying the adhesive to the DLC layer.

In another preferred embodiment, the chemical agent corrosion conditions comprise exposure to a chemical agent selected from the group consisting of: alkaline material, acidic material, salt, sebum, alcohol, ether, ester material or combination thereof.

in another preferred embodiment, the chemical agent comprises an acidic solution, preferably the acidic solution has a pH of 3.0-6.5, more preferably 4.0-5.5.

In another preferred embodiment, the chemical agent comprises an alkaline solution, preferably the alkaline solution has a pH of 7.5-10.5, more preferably 8.0-10.

In a second aspect of the invention, there is provided an adhesive product comprising:

(a) The first base material is a metal base material;

(b) A DLC coating on at least one major surface of the metal substrate;

(c) An adhesive layer adhered to the outer surface of the DLC coating (i.e. the other major surface facing away from the metal substrate); and

(d) optionally a second substrate bonded to the other major surface of said adhesive layer.

In another preferred embodiment, the second substrate is selected from the group consisting of: metal substrates, and non-metal substrates.

In another preferred embodiment, the non-metallic substrate comprises a plastic substrate (e.g., polycarbonate, polyester, etc.).

In another preferred example, the reactive film is a low temperature reactive film (LTR film).

In another preferred embodiment, the non-metallic substrate comprises a plastic.

In another preferred embodiment, the second substrate is a metal substrate.

In another preferred embodiment, the second substrate is a metal substrate and the major surface of the second substrate facing the adhesive layer has a DLC coating deposited thereon.

In another preferred embodiment, the DLC coating on the major surface of the second substrate facing the adhesive layer has a thickness of 0.5 to 20 microns, preferably 1 to 10 microns, more preferably 2 to 6 microns.

In another preferred embodiment, the acidic material comprises an organic acid (e.g., oleic acid), an inorganic acid, or a combination thereof.

In another preferred embodiment, the alkaline substance comprises an organic base, an inorganic base, or a combination thereof.

In another preferred embodiment, the adhesive product has an adhesive strength S1 ≥ 15N/mm between the first substrate and the adhesive layer after storage under humid heat for 3 days²(e.g., 15-25N/mm)²) Preferably not less than 18N/mm²More preferably not less than 20N/mm²Wherein, in the adhesive strength, mm²is the bonding area.

In another preferred embodiment, the adhesive product includes an electronic product, a daily product, a vehicle, or a ship.

In another preferred embodiment, the DLC coating has a thickness of 0.5 to 20 microns, preferably 1 to 10 microns, more preferably 2 to 6 microns.

It is to be understood that within the scope of the present invention, the above-described features of the present invention and those specifically described below (e.g., in the examples) may be combined with each other to form new or preferred embodiments. Not to be reiterated herein, but to the extent of space.

Drawings

Fig. 1 shows the structure of an adhesive structure (or sample) in one embodiment of the invention.

Fig. 2 shows a schematic diagram of a testing apparatus for testing the adhesive strength of an adhesive structure (or specimen) in one embodiment of the invention.

Fig. 3 shows the results of the test of the adhesive strength to the adhesive structure in example 1 of the present invention.

Fig. 4 shows the results of the test of the adhesive strength of the adhesive structure having different coatings in example 2 of the present invention.

Fig. 5 shows the results of the test of the adhesive strength of the adhesive construction under different storage conditions in example 3 of the present invention.

Fig. 6 shows the structure of the adhesive product in an embodiment of the invention, which is identified as follows:

11: a first substrate;

12: a DLC layer on a main surface of the first substrate;

13: an adhesive layer;

14: a second substrate.

fig. 7 shows the structure of the adhesive product in an embodiment of the invention, which is identified as follows:

11: a first substrate;

12: a DLC layer on a main surface of the first substrate;

13: an adhesive layer;

14: a second substrate.

15: a coating on a major surface of the second substrate.

Detailed Description

The present inventors have made extensive and intensive studies and, as a result of extensive screening and trials, have unexpectedly developed for the first time a method capable of significantly improving the adhesive strength between an adhesive and a metal substrate. In particular, the present inventors have found that the formation of a DLC coating ("diamond-like carbon coating") on the surface of a metal substrate can actually significantly improve the adhesive strength between an adhesive (particularly, LTR adhesive) and the metal substrate under hot and humid conditions, even so that the adhesive strength under hot and humid conditions is higher than that under normal conditions (e.g., room temperature conditions). The present invention has been completed based on this finding.

specifically, the present inventors have conducted interfacial mechanical studies and, as a result, have found that deposition of a carbon coating (e.g., a DLC coating) on a metal surface by Physical Vapor Deposition (PVD) or the like allows the bonding strength of an adhesive film (e.g., an LTR film) to be maintained and ensured to the maximum, at least equivalent to or even exceeding the adhesive strength at normal temperature.

Term(s) for

as used herein, the term "DLC coating" refers to a diamond like carbon coating (diamond like carbon layer) formed on the surface of a metal substrate in the present invention. Typically, the DLC coating of the invention is formed directly on the substrate surface by physical vapor deposition or formed in situ.

As used herein, the term "PVD" refers to physical vapor deposition.

as used herein, the term "PU" refers to polyurethane.

As used herein, the terms "adhesive film", "adhesive film" or "tape" are used interchangeably to refer to a film-like tape containing an adhesive, which may be single-sided or double-sided.

As used herein, the terms "adhesive" and "mastic" are used interchangeably.

As used herein, the terms "LTR film" and "low temperature reaction curing type film" are used interchangeably to refer to a low temperature reactive film, a low temperature reactive adhesive film, or a low temperature reactive tape.

High-humidity-heat-resistance bonding structure

The present invention provides an adhesive structure having high resistance to moist heat and/or high resistance to corrosion by chemical agents, comprising:

(a) A first substrate which is a metal substrate and at least one main surface of which is deposited with a DLC coating;

(b) An adhesive layer bonded to said DLC layer, thereby forming a "first substrate-DLC coating-adhesive layer" adhesive structure.

In another preferred embodiment, the adhesive structure of the present invention further comprises a second substrate, wherein the second substrate is bonded to the other major surface of the adhesive layer to form an adhesive structure of "first substrate-DLC coating-adhesive layer-second substrate".

In the present invention, the second substrate may be the same as or different from the first substrate. Typically, the second substrate can be a variety of different metallic substrates, and can also be a variety of different non-metallic substrates.

Representative non-metallic substrates include plastic substrates such as polycarbonate, polyester, and the like.

Representative metal substrates include: a stainless steel substrate, an aluminum substrate, an alloy substrate (e.g., an aluminum alloy, a titanium alloy, a nickel alloy), or combinations thereof.

In the present invention, when the second substrate is a metal substrate, the surface thereof to which the adhesive (or adhesive layer) is adhered may be deposited with a carbon coating (especially a DLC coating), may be free of any coating, or may have other non-carbon coating or non-DLC coating.

In the present invention, experiments have shown that when the surface to be bonded of a substrate is deposited with a carbon coating layer (especially, a DLC coating layer), the ratio of the adhesive strength S1 between the adhesive and the metal substrate in the adhesive structure of the present invention to the adhesive strength S0 between the adhesive and the substrate in the conventional adhesive structure (i.e., "first substrate-adhesive layer") under the same hot and humid conditions is not less than 1.5 (e.g., 2 to 100), preferably not less than 3, more preferably not less than 5, more preferably not less than 10 or more.

In the present invention, the adhesive strength under wet heat condition S1 between the adhesive and the metal substrate in the adhesive structure of the present invention and the adhesive strength under normal temperature (e.g., 4 ℃ or 25 ℃) S0 between the adhesive and the substrate in the conventional adhesive structure (i.e., "first substrate-adhesive layer") (i.e., the first substrate-adhesive layer)_RTThe ratio of (A) is not less than 0.9, preferably not less than 1, more preferably not less than 1.05.

referring to fig. 6 and 7, two exemplary configurations of the adhesive product of the present invention are shown.

In fig. 6, the adhesive product includes: a first substrate (layer) 11, a DLC layer 12 on the main surface of the first substrate, an adhesive layer 13, and a second substrate 14.

In fig. 7, the adhesive product according to the present invention includes: a first substrate (layer) 11, a DLC layer 12 on a major surface of the first substrate, an adhesive layer 13, a second substrate 14, and a coating 15 on a major surface of the second substrate. As for the coating 15, said coating 15 may be a carbon coating (in particular a DLC coating) or else a non-carbon coating or a non-DLC coating.

Reactive membranes

in the present invention, the adhesive film is not particularly limited. Preferred adhesive films are reactive films, such as films (or tapes) of PU-based adhesives. A representative polyurethane adhesive is a PU-isocyanate adhesive, which contains strong polar and chemically active-NCO- (isocyanic acid radical), -NHCOO- (urethane radical) and has excellent adhesive force with various substrates, such as foam, plastic, wood, leather, fabric, paper, ceramic, metal, glass, rubber, plastic, etc.

In the present invention, examples of the reactive adhesive film include (but are not limited to): DE Sa corporation (tesa) low temperature reaction type (LTR) films, such as LTR films of models 58480, 58484, 58486, 58488, 8710, 8714, 8715, 58454.

in addition, one type of typical adhesive film or tape has a thermoplastic component and an isoamino acid vinegar containing component.

Herein, T (melting) is the melting temperature of the thermoplastic component, and T (starting) is the temperature at which the isocyanate component dispersed in the thermoplastic component in the form of particles is capable of reacting with the functional groups of the thermoplastic polyurethane.

As thermoplastic component, preference is given to using OH and/or NH₂A group-functionalized compound. Very preferably, the thermoplastic component comprises at least one semi-crystalline polyester polyurethane.

The reactive adhesive film preferably comprises an anionic, high molecular weight polyurethane dispersion, for example in the form of: commercially available products from the Dispercol U family mentioned above, such as Dispercol l U53, Dispercol l U54, Dispercol lU56, Dispercol U8755, Dispercol U XP 2815, Dispercol VP KA 8758, Dispercol lU XP 2682, Dispercol l U XP 2701, Dispercol U XP 2702, Dispercol U XP 2710 and/or Dispercol BL XP 2578(Dispercol is a registered trademark of Bayer AG).

The reactive adhesive film preferably also comprises tolylene diisocyanate compounds (TDI compounds), such as Dispercoll BL XP2514(TDI Dimer) and/or Aqualink U (dispersion of blocked TDI Dimer) and/or isophorone diisocyanate (IPDI), such as Aqualink D (dispersion of blocked IPDI Trimer) as isocyanate-containing component, dispersed in the thermoplastic component in the form of particles, more particularly finely divided, and substantially deactivated in the particle surface region. The diisocyanates are used, for example, in the form of aqueous suspensions of the corresponding reactive solid isocyanates. Aqualink is available from aquaspots, inc. In particular, the aforementioned diisocyanate products can be used as the crosslinker component in combination with an anionic, high molecular weight polyurethane dispersion as the thermoplastic component (e.g., the Dispercoll U product).

The reactive adhesive film may further contain other formulation ingredients. These ingredients include thickeners, wetting agents, defoamers, fillers (e.g., thermally conductive fillers), pigments, catalysts, aging inhibitors, light stabilizers, and other polymers used to establish specific adhesive properties. The specific adhesive properties can be established, for example, by mixing aqueous dispersions of amorphous polymers (e.g., polyether urethanes or polyacrylates) and/or by mixing aqueous resin dispersions (in particular based on rosin esters).

for the adhesive tape of the invention, at least one layer of a reactive adhesive film can be used, the layer thickness being at least 10 μm and at most 500 μm, preferably at least 20 μm and at most 250 μm.

the adhesive tape that can be used in the present invention is a double-sided adhesive article. Such articles comprising at least one reactive adhesive film are most simply used in the form of a single layer applied to a re-detachable (temporary) carrier material. Suitable temporary carrier materials are all release foils and release papers which are known from the prior art and are provided with a release layer on one or both sides. Siliconized paper is preferred. Two plies of the carrier material that are removable again can also be used, the front and back of the adhesive film being lined, even if the article is not in wound form.

Articles comprising at least one reactive adhesive film may also comprise other carrier materials which remain in the article even after bonding (permanent carrier). For this purpose, foils and papers are likewise suitable, but also scrims (Gelege), textiles (Gewebe) and knits (Gewirke). In each case, the surfaces of these support materials can be subjected, independently of one another, to a chemical pretreatment (primer, plasma) and/or a physical pretreatment (halo, flame, plasma) in order to enable particularly effective anchoring of the reactive adhesive film to the support material. Non-woven fabrics are preferred. The permanent carrier ply reduces any tendency of the partially adhesive film to extrude laterally from the adhesive layer in the molten state under extrusion conditions (in this regard, see DE 102009006935 a 1).

In this preferred case, as nonwoven carrier web a sheet-like structure comprising individual fibers is used. In this context, all nonwoven webs defined according to the DIN EN 29092 standard can be used. The nonwoven web comprises loosely co-laid fibers that are still not joined to each other. The strength comes from the inherent fiber bonding. There is also a distinction between reinforced and non-reinforced nonwovens. The fibers are statistically distributed. The nonwoven may be differentiated by the fibrous material. The fibre materials used may be mineral fibres such as glass, mineral wool or basalt, animal fibres such as silk or wool, vegetable fibres such as cotton, cellulose, chemical fibres such as polyamide, polypropylene, polyphenylene sulphide, polyacrylonitrile, polyimide, polytetrafluoroethylene, aramid or polyester, or mixtures of the aforementioned. The fibers may be mechanically consolidated by needling or water jets, chemically consolidated by the addition of a binder, or thermally consolidated by softening in a suitable air stream, between heated rollers, or in a steam stream.

In a very preferred embodiment of the invention, a cellulose-based nonwoven is used. The basis weight of the nonwoven fabric is preferably 4 to 100g/m²More preferably 10 to 70g/m². Such nonwovens are commercially available, for example, from Glatfelter. The thickness of these nonwovens is preferably from 20 to 100. mu.m, very preferably from 30 to 60 μm.

The adhesive article with the permanent carrier may carry a reactive adhesive film layer with different thickness and/or preferably different kinds of reactive adhesive film layers on the front and back side. In the case of using different reactive adhesive film layers, they both meet the requirements set forth above for reactive adhesive films. In the case of the use of such systems, one of the adhesive layers may also not be reactive, but for example thermoplastic, heat activatable and/or adhesive.

Articles comprising at least one reactive adhesive film may also be used in the form of a bi-layer or multi-layer and without a permanent carrier. At least the uppermost and lowermost layers are reactive adhesive film layers, wherein the layers may differ in thickness and/or type. Where different reactive adhesive film layers are used, they both meet the reactive adhesive film requirements set forth above.

The thickness of the multilayer adhesive article comprising the permanent carrier may be from 50 μm to 1000 μm, preferably from 75 μm to 300 μm.

The reactive adhesive film of the present invention and the adhesive article including at least one layer of the reactive adhesive film may be mass-produced in the form of a web as a roll, a sheet, or a die-cut piece (or a punched article). The reactive adhesive film is preferably non-adhesive at room temperature, since then the material can be very advantageously mass produced (e.g. punched) even without a temporary carrier and can be provided for further processing operations. However, embodiments with adhesive properties are also conceivable.

Typically, the reactive tape of the present invention can be prepared by a conventional method, preferably, the method comprises the steps of:

Drying, in particular suspension drying, the reactive formulation, i.e. the aqueous dispersion;

b1) Coating a temporary or permanent support from the melt with the powder obtained in step a) by a hot-melt, extrusion or calendering process; or

b2) Coating a temporary carrier from the melt with the powder obtained in step a) by a hot-melt, extrusion or calendering process and then affixing a permanent carrier material to the reactive adhesive film thus obtained;

And in the case of permanent carriers

c) Coating the opposite side of the permanent carrier with the same or other potentially reactive formulation, either by repeating steps b1) or b2) against the second side of the permanent carrier or by applying a second non-potentially reactive adhesive directly or indirectly,

Wherein all steps are carried out at a temperature equal to or lower than the starting temperature of the potentially reactive formulation, the process being carried out at a temperature of from 40 ℃ to 100 ℃, in particular at a temperature of from 45 ℃ to 75 ℃.

The temperature difference between T (onset) and T (melting) is preferably 15 ℃ or more.

For drying, suspension drying is particularly preferred, since in this way a potentially reactive formulation in the form of a film is simultaneously obtained. Other drying methods, such as spray drying, are also possible, after which it is advantageous to carry out powderization or granulation of the dried preparation.

In a particularly advantageous process for the manufacture of adhesive articles comprising at least one reactive adhesive film layer, the initially aqueous polyurethane formulation is rendered water-free by suspension drying. The powder thus obtained is applied from the melt at a temperature below the starting temperature of the reactive system, i.e. at 45 ℃ when said starting temperature is 50 ℃ or higher, or at 50 ℃ when said starting temperature is 55 ℃ or higher. For this purpose, a screw extruder is provided as conveying element, which is supplied with the dried polyurethane formulation, for example, as a powder, by means of a solids dosing machine or from a melting vat. The temperature of the melting barrel and the screw extruder is always lower than the starting temperature of the reactive system while conveying, to be precise 45 ℃ when the starting temperature is 50 ℃ or higher, for example, or 50 ℃ when the starting temperature is 55 ℃ or higher, for example.

For coating, contact and non-contact processes can generally be distinguished. For extrusion coating, preference is given to using extrusion nozzles (wide slit nozzles), in which film formation is effected. This process is influenced by the nozzle design inside the paint nozzle. The extrusion nozzles used come from one of three main classes: t-nozzles, fishtail nozzles, and arc-type nozzles. The various types differ in the shape of their fluid channels. In the case of double-or multi-layer adhesive articles, coextrusion nozzles can also be used. In this way all layer thicknesses within the scope of the invention can be achieved.

In a preferred embodiment, the coating is carried out after the nozzle outlet on a temporary support, for example siliconized release paper. The latent reactive adhesive system can be stretched during the coating process. In this case, the degree of stretching is determined by the ratio of the nozzle gap to the film thickness. Stretching always occurs if the layer thickness of the hot-melt adhesive film on the support material to be coated is smaller than the nozzle gap.

In the present invention, the coating temperature is above the melting temperature of the polyurethane, but below the starting temperature of the reactive system.

In order to improve the anchoring on the temporary support, it may be advantageous to apply the reactive adhesive film in a corona manner.

Base material

In the present invention, the first base material is a metal base material. Typical metal substrates include: steel, stainless steel (e.g., various types of stainless steel coded 304, 316, etc.), aluminum, alloys (e.g., aluminum alloys, titanium alloys, nickel alloys, etc.).

For the second substrate, it may be a metal or non-metal substrate. One representative non-metallic substrate is plastic, which includes (but is not limited to): ABS, PC, ABS/PC blends, PMMA, polyamides, glass fiber reinforced polyamides, polyvinyl chloride, polyvinylidene fluoride, cellulose acetate, cyclic olefin copolymers, Liquid Crystal Polymers (LCP), polylactides, polyetherketones, polyetherimides, polyethersulfones, polymethacrylylmethimides, polymethylpentenes, polyphenylene oxides, polyphenylene sulfides, polyphthalamides, polyurethanes, polyvinyl acetates, styrene acrylonitrile copolymers, polyacrylates and polymethacrylates, polyoxymethylene, acrylate styrene-acrylonitrile copolymers, polyethylene, polystyrene, polypropylene, or polyesters (e.g., PBT, PET).

PVD and carbon coating

In the method and the adhesive product of the invention, a significant feature is the provision of a carbon coating, in particular a DLC coating, between the metal substrate and the adhesive layer.

The inventors tried various coating modifications including modification of the surface of a metal substrate with various coatings such as TiAlN coating, CrN coating, TiN coating, etc., but none of them achieved satisfactory resistance to moist heat. However, with carbon coatings (especially DLC coatings deposited by PVD methods), the resistance to wet heat (i.e. maintaining high adhesive strength under wet heat conditions) and chemical corrosion (i.e. maintaining high adhesive strength under chemical immersion or contact) between the adhesive and the metal surface can be significantly improved.

In the present invention, PVD deposition may be performed using conventional PVD equipment to deposit a DLC coating on the surface of the metal substrate to be bonded (i.e., one or both major surfaces of the metal substrate).

Adhesive product

The invention also provides bonded products containing the bonded structures specified in the invention.

typically, the adhesive product of the present invention includes various electronic goods or other products. In their simplest form, they are planar. However, three-dimensional structures are equally suitable, such as housings, glass windows, etc.

The main advantages of the invention include:

(a) The method of the invention is convenient to operate.

(b) With a carbon coating, especially a DLC coating deposited by PVD, the resistance to moist heat between the adhesive and the metal surface can be increased very significantly.

(c) The method of the invention is suitable not only for small-sized components but also for large-sized components.

(d) For an adhesive structure (or an adhesive product) under a damp-heat condition or other severe conditions, it is possible to prevent a decrease in the adhesive strength between the adhesive and the metal surface from being increased very effectively, and even to increase the adhesive strength between the adhesive and the metal surface under a damp-heat condition (compared with the RT condition).

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not noted in the following examples, are generally carried out under conventional conditions or conditions recommended by the manufacturers. Unless otherwise indicated, percentages and parts are percentages and parts by weight.

General procedure

1. base material:

A stainless steel 304 substrate was deposited by physical vapor deposition to form a diamond-like carbon layer.

2. The test method comprises the following steps: push-out force detection method

Tape type: PU base adhesive tape (commercially available from DE Sha model 58484 LTR film)

Bonding a substrate: PC board, and stainless steel with and without DLC coating

Bonding area: 50mm²(mechanical Strength calculation based on this area)

Fitting parameters: 90 ℃ at 4bar for 60s

Residence time: 24 hours, Room Temperature (RT)

Storage conditions were as follows:

The first condition is as follows: moist heat: 60 ℃, 90% relative humidity (r.h.), for 3 days;

And a second condition: thermal cycling: 30 min at-40 ℃ → 30 min at 85 ℃ for 72 cycles

And (3) carrying out a third condition: room temperature (relative humidity 50%)