DE102010041521A1 - Reactive hot melt adhesive composition and use thereof - Google Patents

Abstract

The present invention relates to hot-melt adhesive compositions containing, based in each case on the total weight of the composition, the components (a) 20% by weight to 98.9999% by weight of at least one thermoplastic base polymer; (b) 1% to 75% by weight of at least one resin; (c) 0.0001% by weight to 5% by weight of at least one laser light absorbing additive. The invention further relates to the use of such compositions.

Description

The present invention relates to hot melt adhesive compositions and their use.

Hot melt adhesives are nowadays widely used in the wood processing industry, the automotive industry as well as in textile lamination. Normally, the hot melt adhesive is melted and applied to a first substrate. In general, a second substrate is immediately, d. H. before the hot melt adhesive has cooled, laminated. In many cases, however, it may be advantageous to only pre-coat the first substrate with the hot-melt adhesive and to perform the bonding of the second substrate at a later time ("reactivation method"). The advantage of the reactivation process is that the processor does not need any adhesive processing machines when working with substrates pre-coated with adhesive.

Even with frequent change of substrates to be bonded, z. As in other geometries, colors and substrates, it may be useful for the user to work with precoated substrates, as this conversion times can be saved by changing the adhesive. Such precoating methods are known in the art.

So z. B. worked in the furniture industry often with pre-coated edges. Even with the lamination of paper foils on tensioning and MDF boards, pre-coated paper foils are used. In the prior art, the activation of the hot melt adhesive takes place by adhesive-side heating by means of IR radiators, hot air blower or back heating by means of a hot roller.

A disadvantage of these prior art processes is that the reactivation not only heats the adhesive but also the substrate and expands. Upon cooling (after bonding the second substrate), the first substrate then shrinks again, which can lead to optical defects in the finished parts.

In addition, the heat supplied during reactivation must be dissipated again after bonding to the second substrate (eg via cooling rolls), since otherwise joint openings may occur. In addition, there may be a limitation in the choice of the reactivation temperature for thermally sensitive materials (eg plastics), since otherwise the substrates may be damaged.

In recent years, methods have been developed in which the hot melt adhesive layer is selectively activated by means of laser beams.

In EP-A 1852242 a hot melt adhesive layer is applied to a cover strip by coextrusion. Disadvantage is, however, that commercially available hot melt adhesives can be reactivated by laser light only poorly because they do not absorb enough energy in the wavelength range of commercial laser.

WO-A 2009/026977 describes edge strips for furniture that has a melt layer, but with no reference to a hot melt adhesive.

It is therefore an object of the present invention to provide a hot melt adhesive which at least partially overcomes the disadvantages of the prior art and exhibits a significantly improved reactivity by laser radiation compared with the prior art.

• (a) 20 Gew.-% bis 98,9999 Gew.-% mindestens eines thermoplastischen Basispolymers;
• (b) 1 Gew.-% bis 75 Gew.-% mindestens eines Harzes;
• (c) 0,0001 Gew.-% bis 5 Gew.-% mindestens eines Laserlicht absorbierenden Additivs.

The object is achieved by a hot melt adhesive composition containing in each case based on the total weight of the composition, the components

• (a) from 20% to 98.9999% by weight of at least one thermoplastic base polymer;
• (b) 1% to 75% by weight of at least one resin;
• (C) 0.0001 wt .-% to 5 wt .-% of at least one laser light absorbing additive.

It has been shown that the use of component (c) results in a hot-melt adhesive composition which can be sufficiently reactivated by means of laser light, which in particular can contain pigments such as TiO ₂ .

Reactivation means the transfer of at least part of the hot melt adhesive composition surface according to the invention into the molten state, which is to serve as an adhesive bond during the bonding.

Component (c) contains one, two or more than two laser light absorbing additives. Preferably, component (c) consists of only one additive.

Preferably, the at least one laser light absorbing additive is an optionally doped tin oxide such. Example, antimony or indium tin oxide (ATO or ITO), a metal boride, a rylene, copper hydroxide (KHP), based on bismuth oxychloride, lanthanum hexachloride, metal oxide coated mica, carbon black or a mixture of two or more of these additives.

The at least one laser light absorbing additive absorbs the laser light and converts the electromagnetic energy into heat for the most part. This makes it possible to specifically heat only the adhesive joint, without the substrates to be bonded are unnecessarily thermally stressed.

Exemplary laser light absorbing additives such as a doped tin oxide, e.g. B. antimony or indium tin oxide (ATO or ITO), rylene derivatives, copper hydroxide phosphate (KHP), pigments based on bismuth oxychloride, lanthanum hexachloride, metal oxide coated mica, carbon black or other laser light absorbing substances are known from the prior art.

Preferably, the at least one laser light absorbing additive has an absorption spectrum that can absorb laser light in the non-visible range. Such additives are available, for example, from BASF SE under the designation Lumogen IR765, Lumogen IR 788 and Lumogen IR 1050. Lumogen IR 765 and Lumogen IR 788 are based on Rylene, while Lumogen IR 1050 is a nanoparticulate suspension of a heavy metal pigment.

Furthermore, the pigments of the Iriodin LS series from Merck can be used. These are metal oxide coated mica.

Accordingly, particularly preferred laser light absorbing additives are rylenes, heavy metal pigments or metal oxide coated mica. In particular, rylenes or heavy metal pigments are preferred.

Lumogen IR 1050 is particularly preferred for the purposes of the present invention. Lumogen IR 1050 also absorbs laser light in the common wavelength range of 940/980 nm and 1064 nm. Thus very low-energy diode lasers can also be used. In addition, Lumogen IR 1050 does not significantly affect either the color of the hotmelt adhesive composition or its other properties, at least for small quantities.

Accordingly, it is preferred that the at least one laser light absorbing additive has at least one absorption maximum in the range from 900 nm to 1300 nm.

The hotmelt adhesive composition according to the invention comprises component (c) with a weight fraction based on the total weight of the composition of from 0.0001% by weight to 5% by weight, which is preferably distributed homogeneously in the composition. The proportion is preferably from 0.001% by weight to 1% by weight, more preferably from 0.01% by weight to 0.5% by weight, more preferably from 0.01% by weight to 0.2% by weight. -%.

Component (a) contains one, two or more than two thermoplastic base polymers. Preferably component (a) comprises an ethylene-vinyl acetate copolymer (EVA), a polyolefin homopolymer, polyolefin copolymer or a polyolefin interpolymer. But also thermoplastic polyesters, polyamide copolymers or thermoplastic rubbers can be used. These may be used as mixtures, with a mixture containing EVA being preferred. Particularly preferred are EVA copolymers.

In the context of the present invention, the polyolefins are polymers of C ₂ -C ₁₈ olefinically unsaturated hydrocarbon compounds. The olefinically unsaturated hydrocarbon compounds may be linear, branched or even cyclic. Polyolefin homopolymers, copolymers and terpolymers can be used. In general, the polyolefins to be used are polymers based on ethylene and one or two further different C ₃ -C ₁₈ olefinically unsaturated hydrocarbon compounds.

As an EVA copolymer z. For example, the Escorene types of Exxon and Evatane types of Elf-Atochem can be used. The vinyl acetate contents can vary, for example, from 10% by weight to 40% by weight, based on the copolymer, preference being given to using types having a vinyl acetate content of from 18% by weight to 33% by weight. Melt Indices (MFI) may be, for example, 6-800 g / 10 min [190 ° C; 2.16 kp].

As a polyolefin polymer, for. For example, available from the company Evonik Vestoplast types are used. Vestoplast types are co- and terpolymers of ethylene with propylene and butylene. Furthermore, narrow molecular weight distribution polyolefins (based on metallocene catalysts) such as Affinity grades from Dow and Engage grades from DuPontDow or Exxon's Exact grades can also be used. The Affinity series metallocene-based polymers are copolymers of ethylene and 1-octene.

The proportion by weight of component (a) is from 20% by weight to 98.9999% by weight, based on the total weight of the composition. The proportion is preferably from 20% by weight to 70% by weight, more preferably from 25% by weight to 65% by weight.

Component (b) contains one, two or more than two resins.

The resins are said to increase the hot tack of the hot melt adhesive composition and thereby improve adhesion to the substrates to be bonded. Permanent bonding is often possible only by using such resins. Accordingly, higher quality bonds can generally be achieved by additional use of these resins.

Preferably, component (b) contains resins selected from the group of resins consisting of aliphatic, aromatic and aliphatic-aromatic hydrocarbon resins, modified (eg hydrogenated) hydrocarbon resins, modified terpene resins, natural resin esters such as rosin esters and tall resin esters. Suitable, preferably aromatic resins can be selected, for example, from Novares resins from Rüttgers Chemicals. Aliphatic or aromatic modified aliphatic resins may preferably be obtained from Exxon Mobil (Escorez 1000 and 2000 series). Examples of hydrogenated aliphatic resins which can be used according to the invention are the resins of the Escorez 5000 series from Exxon. Natural resin esters are offered, for example, by the company Arizona ("Sylvatac series"). Modification of resins is carried out, for example, by hydrogenation.

In particular, in the case where the component (a) contains EVA, preferably aromatic, or aliphatically modified non-hydrogenated resins or natural resin esters are used.

In particular, in the case where the component (a) contains a polyolefin, it is preferable to use aliphatic, aromatic-modified aliphatic or hydrogenated hydrocarbon resins.

The proportion by weight of component (b) is 1 wt .-% to 75 wt .-% based on the total weight of the composition. Preferably, the proportion is 5 wt .-% to 60 wt .-%, particularly preferably from 10 wt .-% to 50 wt .-%.

• (d) enthaltend mindestens ein Wachs;
• (e) enthaltend mindestens einen Füllstoff;
• (f) enthaltend mindestens ein Additiv, das verschieden von den Komponenten (a) bis (e) ist.

Preferably, the composition according to the invention additionally contains one or more of the components:

• (d) containing at least one wax;
• (e) containing at least one filler;
• (f) containing at least one additive which is different from the components (a) to (e).

The composition according to the invention can therefore additionally only (d), only (e), only (f), (d) and (e), (d) and (f), (e) and (f) or (d), ( e) and (f) included.

Component (d) contains one, two or more than two waxes. The waxes can be selected from the group of synthetic waxes, Fischer-Tropsch waxes, paraffin waxes, microcrystalline waxes, natural waxes and chemically modified waxes (eg MSA-grafted waxes). Examples of waxes are the types Paraflint H2 (from Sasol, Fischer-Tropsch wax) and the polyethylene wax Vestowax H616 from Evonik AG. Preferably, Fischer-Tropsch waxes or PE waxes are used.

If component (d) is present, the proportion by weight of component (d) is from 0.5% by weight to 10% by weight, based on the total weight of the composition. Preferably, the proportion is 1 wt .-% to 5 wt .-%.

Component (e) contains one, two or more than two fillers. Preference is given to inorganic fillers. Examples of fillers are chalk, silicates, clays, talc, barite and light latex. Preference is given to using chalk as filler.

If component (e) is present, the proportion by weight of component (e) is from 5% by weight to 70% by weight, based on the total weight of the composition. The proportion is preferably from 10% by weight to 50% by weight.

The component (f) contains one, two or more additives different from the components (a) to (e). Examples are stabilizers, anti-aging agents, UV stabilizers, plasticizers, pigments and solvents.

If component (f) is present, the proportion by weight of component (f) is from 0.01% by weight to 5% by weight, based on the total weight of the composition. Preferably, the proportion when using one or more stabilizers is not more than 2 wt .-%.

The sum of the weight fractions of the individual components, that is to say at least (a), (b), (c), in the composition adds up to 100% by weight. If one or more of the components (d), (e), (f) or other components are present, the sum corresponding to this 100% by weight results accordingly.

If a chemical substance can be assigned to more than one component, it is assigned in alphabetical order beginning with component (a).

Compositions according to the present invention can be used in all applications in which the precoating of the substrates to be bonded is possible and makes sense technically and commercially. In particular, here is the textile lamination, Bonding in the automotive sector as well as bonding in the wood and furniture industry called. In the case of bonding in the wood industry, the flat lamination of precoated furniture foils, or the sheathing of precoated furniture foils, should be mentioned here in particular. The present invention is particularly suitable for the bonding of pre-coated furniture edges.

Another object of the present invention is accordingly the use of the hot melt adhesive composition according to the invention for Reaktivierverklebung, especially in the textile industry, for lamination in the automotive sector and to bonding in the wood and furniture industry. Preference is given to the use for the flat lamination of precoated furniture foils, the sheathing of pre-coated furniture foils or for the bonding of pre-coated furniture edges.

Hotmelt adhesive compositions according to the invention, which are used in the area of cladding and flat lamination of furniture films, preferably have viscosities of 5,000 mPas to 100,000 mPas at 160 ° C., more preferably between 10,000 mPas and 50,000 mPas at 160 ° C.

Hot melt adhesive compositions according to the invention which are used in the area of edge pre-coating preferably have viscosities of from 30,000 mPas at 180 ° C. to 250,000 mPas at 180 ° C., more preferably between 50,000 mPas and 200,000 mPas at 180 ° C.

By selecting suitable raw materials which are known to the person skilled in the art, the softening range of the hot melt adhesive compositions according to the invention can be varied within a wide range. The softening range may affect the later heat resistance of the product made with the hot melt adhesive composition of the present invention. In compositions according to the invention whose component (a) contains EVA, this is preferably between 70 ° C and 130 ° C, more preferably between 80 ° C and 120 ° C; in polyolefins, the softening range is preferably between 120 ° C and 170 ° C, more preferably between 130 and 165 ° C.

The hot melt adhesive compositions of the invention are solid at room temperature and preferably tack-free. Preferably, the hot melt adhesive compositions according to the invention are block-free after a relatively short time, so that the substrates coated with them can be stacked on one another or can be wound up.

The hot melt adhesive composition according to the invention is prepared by the prior art known in the art, for. B. produced by kneaders or extruders. The hot melt adhesive composition of the invention is preferably granulated by known technology. But it is also a block filling conceivable.

The hot melt adhesive composition according to the invention is generally applied to a substrate to be coated at a hot melt adhesive temperature of 140-220 ° C. The order is preferably carried out by means of roller, hot rack, nozzles or slot nozzles. The amount of hot melt adhesive may preferably vary from 20 g / mm ² to 250 g / mm ² . For melting all known on the market for hot melt adhesives suitable devices can be used.

The substrates to be coated may be all types of textile materials, plastics, metals, wood and wood-based materials. The substrates can be present as plate goods as well as rolls. When coating temperature-sensitive materials such. B. plastics are chosen as low adhesive application temperatures.

The reactivation of the hotmelt adhesive composition and the bonding to the second substrate takes place at a later time. The reactivation of the hot melt adhesive composition according to the invention is carried out using commercially available lasers, for. B. with semiconductor lasers, diode lasers, solid state lasers, or gas lasers.

The second substrate may in turn be a textile material, a plastic, a metal, wood or a wood material.

The activation by means of the laser advantageously leads only to a pulse-like heating of the hotmelt adhesive composition. The substrates that do not absorb the laser light are practically not heated. As a result, thermal damage to the hotmelt adhesive composition according to the invention and to the substrates to be bonded can be virtually ruled out. This plays a major role, especially in temperature-sensitive plastic substrates. Due to the low thermal load of the hotmelt adhesive composition, it is also possible to avoid an odor nuisance which can occur when using hotmelts according to the prior art.

Another advantage of the hot melt adhesive composition according to the invention is also associated with the very well-defined heating of the hot melt adhesive layer. In the prior art the hotmelt adhesive is heated and reactivated by means of IR radiators, hot air or the like.

It can not be avoided that the substrate on which the adhesive is also heated. Upon cooling (after bonding to the second substrate), the first substrate then shrinks again, which can lead to optical defects in the finished parts.

When bonding furniture edges, the adhesive is usually applied by means of an applicator roll on the narrow side of a clamping plate and the edge glued to it. This always leaves a small adhesive joint visible, which can then absorb dirt and thus becomes visible. In addition, moisture can penetrate into the furniture part over this gap and damage the furniture part. By contrast, when using the adhesive composition according to the invention, almost no glue joint remains visible. The moisture sensitivity is noticeably reduced.

example

Edge-melt adhesive according to the prior art:

• 55.0% Escorene UL02528
• 30.0% Novarez TN120
• 14% CaCO ₃ filler
• 1% Vestowax 616

EVA-based edge melt adhesive composition according to the invention:

• 55.0% Escorene UL02528
• 30.0% Novarez TN120
• 13.9% CaCO ₃ filler
• 1.0% Vestowax 616
• 0.1% Lumogen IR 1050

Escorene UL02528 is an EVA from the company Exxon with 28% VA content and an MFI of 25 g / 10 min, Novarez TN120 is an aromatic resin from Rüttgers with a softening point of about 115 ° C. Vestowax 616 is synthetic hard wax from Evonik AG. Lumogen IR 1050 is a laser light absorbing additive from BASF AG based on a metal oxide.

The hot melt adhesive composition according to the invention has a viscosity of about 150,000 mPas at 180 ° C and a softening point of 90 ° C. The adhesive without the laser light absorbing additive of the prior art has a practically identical viscosity and an identical softening point.

The hot melt adhesive composition according to the invention was applied to an ABS plastic edge by means of a slot die and wound up. The coating weight was about 200 g / m ² .

The thus pre-coated edge was subsequently applied to the narrow side of a chipboard on an edgebander from Homag. The hotmelt adhesive layer was reactivated by means of a diode laser with the wave length 980. The laser power that was necessary to achieve good edge bonding was 1200 watts. By comparison, in the case of edges pre-coated with an edge-melt adhesive according to the prior art, good adhesion could not be achieved even with a laser power of 3000 watts, since the adhesive layer heated the laser light only insufficiently. In addition, damage to the edges occurred at this high laser power.

Compared to the prior art, the adhesive joint is clearly less visible. A water storage of the parts produced according to the present invention showed that the water resistance could be significantly improved over the prior art.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1852242 A [0008]
• WO 2009/026977 A [0009]

Claims (19)

Hot melt adhesive composition containing in each case based on the total weight of the composition, the components (a) from 20% to 98.9999% by weight of at least one thermoplastic base polymer; (b) 1% to 75% by weight of at least one resin; (C) 0.0001 wt .-% to 5 wt .-% of at least one laser light absorbing additive. A composition according to claim 1, characterized in that the additive absorbing at least one laser light is an optionally doped tin oxide, a metal boride, a rylene, copper hydroxide phosphate, a bismuth oxychloride based pigment, lanthanum hexachloride, a metal oxide coated mica, carbon black or a mixture of two or more thereof Additive is. A composition according to claim 1 or 2, characterized in that the at least one laser light absorbing additive is a rylene, a heavy metal pigment or metal oxide coated mica. Composition according to one of claims 1 to 3, characterized in that the at least one laser light absorbing additive has an absorption spectrum that can absorb laser light in the non-visible range. Composition according to one of claims 1 to 4, characterized in that the at least one laser light absorbing additive has at least one absorption maximum in the range of 900 nm to 1300 nm. Composition according to any one of Claims 1 to 5, characterized in that the proportion by weight of component (c) is in the range from 0.001% to 1% by weight. Composition according to any one of Claims 1 to 6, characterized in that component (a) comprises at least one ethylene-vinyl acetate copolymer or a polyolefin homo-, co- or terpolymer. Composition according to any one of Claims 1 to 7, characterized in that component (a) comprises at least one ethylene-vinyl acetate copolymer. Composition according to any one of Claims 1 to 8, characterized in that the composition is tack-free at room temperature. Composition according to any one of Claims 1 to 9, characterized in that component (b) comprises at least one aliphatic, aromatic or aliphatic-aromatic hydrocarbon resin, modified (eg hydrogenated) hydrocarbon resin, modified terpene resin or a natural resin ester. Composition according to one of Claims 1 to 10, characterized that these additionally one or more of the components (d) containing at least one wax; (e) containing at least one filler; (f) containing at least one additive which is different from components (a) to (e), contains. A composition according to claim 11, characterized in that the at least one filler is chalk. Composition according to Claim 11 or 12, characterized in that the at least one wax is a Fischer-Tropsch or a polyethylene wax. Composition according to any one of Claims 11 to 13, characterized in that the at least one additive is a stabilizer. Use of a composition according to one of claims 1 to 14 for Reaktivierverklebung by means of a laser. Use according to claim 15 in the textile industry or the automotive industry. Use according to claim 15 in the wood and furniture industry. Use according to one of claims 15 to 17 for the flat lamination of precoated furniture foils or the sheathing of precoated furniture foils. Use according to one of claims 15 to 17 for the bonding of pre-coated furniture edges.