NL2011815C2

NL2011815C2 - Hot melt adhesive composition.

Info

Publication number: NL2011815C2
Application number: NL2011815A
Authority: NL
Inventors: Rudolph Frank Block; Erik Bouwman
Original assignee: Saba Dinxperlo B V
Priority date: 2013-11-18
Filing date: 2013-11-18
Publication date: 2015-05-19
Also published as: WO2015072860A1

Abstract

The present invention is in the field of a hot melt adhesive composition, use of said hot melt composition and products comprising said composition. A hot melt adhesive (HMA), also known as a hot glue is a form of thermoplastic adhesive. It is commonly supplied in solid form, as blocks, pillows, powders, films or sticks designed to be melted e.g. in an dedicated hot melt melter and to be applied using a hot melt applicator. Such a glue i tacky when hot, and solidifies in a relatively short time, typically from a few seconds to one a few minutes. Hot melt adhesives can also be applied by dipping or spraying.

Description

Title Hot melt adhesive composition FIELD OF THE INVENTION

The present invention is in the field of a hot melt adhesive composition, use of said hot melt composition and products comprising said composition.

BACKGROUND OF THE INVENTION A hot melt adhesive (HMA), also known as a hot glue, is a form of thermoplastic adhesive. It is commonly supplied in solid form, as blocks, pillows, powders, films or sticks designed to be melted e.g. in an dedicated-hot melt melter and to be applied using a hot melt applicator. Such a glue is tacky when hot, and solidifies in a relatively short time, typically from a few seconds to a few minutes exceptionally. Hot melt adhesives can also' be applied by dipping or spraying.

Hot melt adhesives provide several advantages. Volatile organic compounds are reduced or eliminated, a drying or curing step is eliminated, they have a long shelf life, they do not lose thickness during solidifying, and usually can be disposed of without special precautions. They also have some disadvantages, such as a thermal load (due to hot application) of a substrate, loss of bond strength at higher temperatures, and complete melting of the adhesive.

General properties of hot melt adhesives are open time (working time to make a bond, where the surface still retains sufficient tack, can range from seconds for fast-setting adhesives to infinity for pressure-sensitive adhesives), set time (time to form a bond of acceptable strength), tack (degree of surface stickiness of the adhesive, and surface energy (influences wetting of different kind of surfaces).

Hot melt glues often consist of one base material with various additives. The composition is then formulated to have a glass transition temperature (onset of brittleness) below a lowest service temperature and a suitably high melt temperature as well. Hot melt adhesives can be tailored for a given application, e.g. the melt viscosity, tack, strength and the crystallization rate (and corresponding open time) and crystallization level. It is considered that a lower level of crystallization, such as can be reached by using amorphous polymers will lead to softer adhesives such as which can be used for bonding soft and flexible materials.

Some of the possible base materials, each having advantages and disadvantages, are ethylene-vinyl acetate (EVA) copolymers, ethylene-acrylate copolymers, polyamides and polyesters, polyurethanes (PUR), or reactive urethanes, styrene block copolymers (SBC), also called styrene copolymer adhesives and various other copolymers.

Polyolefins, such as polyethylene, suffer from various disadvantages, e.g. from cohesive failure, and relative high cost price.

In physical and organic chemistry, the dispersity is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called monodis-perse or uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsistent size, shape and mass distribution is called polydisperse or non-uniform. The objects can be in any form of chemical dispersion, such as particles in a colloid, and polymer molecules in a solvent. Polymers can possess a distribution of molecular mass; and particles often possess a wide distribution of size, surface area and mass.

The term dispersity, represented by the symbol B, can refer to either molecular mass or degree of polymerization. It can be calculated using the equation DM = Mw/Mn, where Mw is the weight-average molar mass and Mn is the number-average molar mass.

Many of the prior art adhesives need to be bonded directly, typically within a few seconds, as an open time is relatively short. That characteristics makes such an adhesive not suited for larger surfaces to be adhered.

It is also preferred to have an adhesive that has a long transferability.

It is often also important to have a high initial strength. For many prior art adhesive initial strength is not sufficient. One has to wait before making the bond thus reducing open time.

For many applications a strong initial bond is required. Inherently it is difficult to provide a strong bond with an adhesive, especially with hot melt adhesives.

Adhesives are preferably also temperature stable.

It is therefore an object of the present invention to provide a hot melt adhesive which overcomes one or more of the above disadvantages, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates to a hot melt adhesive according to claim 1, a use thereof according to claim 12 and a product according to claim 14. The present hot melt is considered to be a relatively slow hot melt.

The present adhesive surprisingly provides a high initial strength, suitable viscoelastic properties, strong bonding, long transferability, good wetting, low-temperature flexibility, good anti-blocking, good stability, long shelf life, stress release during formation of a bond, applicability over a broad temperature range, application on a variety of substrates, such as porous flexible substrates, good cohesive strength, and long open time, and which can be used in combination with a broad range of additives, organic compounds and elastomers, respectively, compared to other adhesives, especially hot melt adhesives. The present hot melt adhesive provides an open time of at least 10 seconds, more typically at least 3 minutes, and often at least 5 minutes. It is therefore especially suited for application on relatively large surfaces, such as in a matrass, in foam and in furniture. It is very suited for difficult-to-bond plastics. It provides a very good adhesion, such as to polypropylene and products comprising polypropylene, such as foam, as well as for wood and metal bonding.

The present adhesive comprises a C5-C50 organic compound, such as a C6-C25 organic compound. This organic compound can unexpectedly be added in high amounts to the present adhesive, without jeopardizing functionality thereof; in fact it has been found that the organic compound even improves the functionality. The organic compound is preferably a liquid compound.

The present adhesive comprises a synthetic thermoplastic polymer having weight average molecular weight of · 80,000 to 200,000 and a dispersity of 1-4.2, preferably from 1-3.5, more preferably from 1-3, even more preferably from 1- 2.5, such as from 1.1-2, wherein the dispersity is defined as above (DM = Mw/Mn, where Mw is the weight-average molar mass and Mn is the number-average molar mass). For prior art adhesive it is considered necessary to have a high dispersity polymer, typically a DM of about 5 or higher, in order to obtain required characteristics, such as good adhesive properties. It therefore came as a surprise that relatively low dispersity polymers could be used. In fact these low dispersity polymers, albeit available on the market, are put on the market for very different uses, such as non-woven fabrics, resin modifiers, elastics and pigment-dispersing agent.

The present adhesive further comprises an elastomer and preferably a wax.

In view of the present invention the following is considered relevant.

Amorphous polyolefin (APO/APAO) polymers are compatible with many solvents, tackifiers, waxes, and polymers; they find wide use in many adhesive applications. APO hot melts have good fuel and acid resistance, moderate heat resistance, are tacky, soft and flexible, have good adhesion and longer open times than crystalline polyolefins. APOs tend to have lower melt viscosity, better adhesion, longer open times and slow set times than comparable EVAs. Some APOs can be used alone, but often they are compounded with tackifiers, waxes, and plasticizers (e.g., mineral oil, poly-butene oil). Examples of APOs include amorphous (atactic) propylene (APP), amorphous propylene/ethylene (APE), amorphous propylene/butene (APB), amorphous propylene/hexene (APH), amorphous propyl-ene/ethylene/butene. APOs show relatively low cohesion, the entangled polymer chains have fairly high degree of freedom of movement. Under mechanical load, most of the strain is dissipated by elongation and disentanglement of polymer chains.

Thereby the present invention provides a solution to one or more of the above mentioned problems.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a hot melt adhesive composition according to claim 1.

The elastomer is present in a relative low amount. It preferably has a molecular weight of 20-150 kg/mole, more preferably 30-100 kg/mole, such as 50-70 kg/mole. It has been found that especially this molecular weight range provides good characteristics to the present adhesive.

In an example of the present adhesive the organic compound is selected from liquid alkanes, alkenes, aromatic hydrocarbons having 1-5 aromatic groups, such as 3-4 aromatic groups, such as naphthalene, oils, such as light and middle weight oils, mineral oil, naphthenic oils, poly-butene oil, and combinations thereof. Naphthenic oils may relate to hydrotreated heavy naphthenic distillate. It may have' less than 50% non-aromatic hydrocarbons. A broad range of organic compounds may be used in the present adhesive.

In an example of the present adhesive the organic compounds is present in an amount of 5-60 wt.%, preferably 10-50 wt. %, more preferably 20-45 wt. %, such as 30-40 wt.%.

Such is considered a very high amount. As noted addition of an organic compound is thereby hardly limited; further the characteristics of the present adhesive remain good.

In an example of the present adhesive the synthetic polymer is one or more atactic polymers, preferably a metallocene catalyst based atactic polymer, more preferably a poly(alfa)alkene polymer, such as poly(alfa)propylene, poly(alfa)butadiene, poly(alfa)methylpentene, most preferably more than 80 wt.% polypropylene. It is even more preferred to use 85 wt.%-99.99 wt.% polypropylene, such as 90 wt.%-99 wt.% polypropylene. Small amounts of other polymers may be present.

In an example of the present adhesive the synthetic polymer is present in an amount of 10-40 wt.%, preferably 12-30 wt. %, more preferably 15-25 wt. %, such as 18-22 wt.%.

Best performances in terms as described above are found for these adhesives.

In an example of the present adhesive the synthetic polymer is 70-100% atactic, preferably 90-99.99% atactic, more preferably 95-99.9% atactic, such as 98-99% atactic. Surprisingly highly atactic polymers with low polydispersity may be used in adhesives, especially in relative high amounts.

In an example of the present adhesive the elastomer is one or more of a copolymer, a block polymer, and a homopolymer, preferably a styrene block polymer.

These elastomers preferably have a tri-block structure, such as an A-B-A or A-B-C structure. A central block B is preferably chemically more flexible whereas block A and C are chemically more inflexible. The A- and/or C-block preferably have a glass transition temperature that is above ambient temperature, preferably a glass transition temperature somewhat lower than a temperature of application, whereas B-blocks preferably have a glass transition temperature that is around or below ambient temperature. The present elastomer preferably has one or more of the characteristics: being macromolecular; a glass transition temperature (of at least a part thereof) Tg is below a temperature of application; being amorphous; having a moderate degree of crosslinking; and having low secondary forces between molecules.

In an example of the present adhesive the elastomer is present in an amount of 1-15 wt.%, preferably 2-10 wt. %, more preferably 3-8 wt. %, such as 4-6 wt.%.

In an example of the present adhesive the elastomer is one or more of a natural rubber, an-artificial rubber, such as a styrene-isoprene-styrene block copolymer, a styrene-butadiene-rubber, a styrene-butadiene-styrene block copolymer, a styrene-ethylene-butadiene-styrene block copolymer, a sty-rene-isoprene- butadiene-styrene block copolymer, a nitril-isoprene rubber, and isoprene-isoprene rubber.

Examples are styrene-butadiene-styrene (SBS), providing high-strength, styrene-isoprene-styrene (SIS) providing low-viscosity and high initial strength, styrene-ethylene/butylene-styrene (SEBS) providing low self-adhering, and styrene-ethylene/propylene (SEP).

In an example the present adhesive comprises one or more additives.

Additives may relate to a wax, such as microcrystalline waxes, fatty amide waxes, PE-waxes, and PP-waxes; to a plasticizer, such as a paraffin oil, polyisobutylene, naphthenic oil, and a chlorinated paraffin; to an antioxidant and stabilizer; to a pigment and dye; and to a tackifying resin, such as a terpene-phenol resin, a rosins, a terpene and a modified terpene, an aliphatic, cycloaliphatic and aromatic resin, a hydrogenated hydrocarbon resin, tackifier resin emulsion, modified rosin resin, polymerized rosin resin, a-pinene resins, β-pinene resins, terpene resins, terpene phenol resins, alkylphenol resins, styrene resins, xylene resins, couma-rone resins, indene resins, hydrocarbon resins and combinations thereof, and their derivates, and their mixtures.

In an example the present adhesive comprises 0.01-30 wt. % wax, preferably 1-2 wt. %, such as paraffin. The wax is preferably high crystalline short chain was, such as a C2-C5 polymer wax, wherein a melting point of the wax is preferably lower than 100 °C, more preferably lower than 90 °C.

In an example of the present adhesive comprises 0.01-50 wt. % resin, preferably 1-30 wt. %.

In an example of the present adhesive comprises 0.01-5 wt. % plasticizer, preferably 1-2 wt. %.

In an example of the present adhesive comprises 0.01-5 wt. % stabilizer, preferably 0.1-1 wt. %.

In a second aspect the present invention relates to a use of the present adhesive composition for one or more of obtaining a high initial strength, low quantity, long transferability, and long open time.

The present hot melt adhesives may be used for corrugated fiberboard boxes, disposable diaper, paperboard cartons, assembly of parts in manufacturing, and in electronic devices .

In an example the present adhesive composition is used in one-sided or two-sided bonding, especially of bonding of large surfaces of 0.5-10 m2, such as 1-5 m2, such as in a matrass, in foam and in furniture.

In a third aspect the present invention relates to a product comprising an adhesive composition according to the invention.

The invention is further detailed by the accompanying figures and examples, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

EXAMPLES/EXPERIMENTS

The invention although described in detailed explanatory context may be best understood in conjunction with the accompanying examples and figures.

Example 1: 4910 comparison with commercial hot melt based on APAO with high (poly)dispersity

The performance of the present adhesive was compared with a standard APAO based hot melt, i.c. Sabamelt 4910. The test involved using a spray gun to glue together foam under tension at different open times. The present adhesive is bonded securely within 15 seconds and typically less, and was substantially faster than the commercial hot melt which required 30 seconds till 1 minute. The open time of the present adhesive averaged 3 minutes, substantially longer than the commercial hot melt (2 minutes). Thus showing that the use of a APAO of low (poly)dispersity in combination with a elastomer and an organic compound creates at the customer a much broader application window, which is less dependent on mass (e.g. beads of 1,5-5 g/m) and settings, generating a robust process.

Example 2:

Example comparing different organic compounds:

Properties like viscosity, compatibility, initial strength, open time, were tested.

Examples 3 and 4 demonstrate the importance of the organic compound and the chemical nature of this compound.

It should be appreciated that for commercial applica- tion it may be preferable to use one or more variations of the present system, which would similar be to the ones disclosed in the present application and are within the spirit of the invention .

Claims

A hot melt composition comprising 1-66 wt. % of a C5 -C50 organic compound, 5-50 wt. % of a synthetic thermoplastic polymer with a weight average molecular weight (Mw) of 80,000 to 200,000 and a dispersity of 1-4.2, and 0.1-20 wt. % of an elastomer, preferably with a molecular weight of 20-150 kg / mol, the wt. % is based on the total weight of the composition.

Hot melt composition according to claim 1, wherein the organic compound is selected from liquid alkanes, olefins, aromatic hydrocarbons with 1-5 aromatic groups, such as 3-4 aromatic groups, such as naphthalene, oils such as light and medium oils, mineral oils, naphtha -nic oils, polybutene oil, and combinations thereof.

Hot melt composition according to claim 1 or 2, wherein the organic compounds are present in an amount of 5-60 wt. %, preferably 10-50 wt. %, more preferably 20-45 wt. %, such as 30-40 wt. %.

Hot melt composition according to any of claims 1-3, wherein the synthetic polymer is one or more atactic polymers, preferably a metallocene catalysis based atactic polymer, preferably a poly (alpha) olefin polymer, such as poly (alpha) propylene, poly (alpha) butadiene, poly (alpha) methylpenentene, preferably more than 80 wt. % polypropylene.

The hot melt composition according to any one of claims 1-4, wherein the synthetic polymer is present in an amount of 10-40 wt. %, preferably 12-30 wt. %, more preferably 15-25 wt. %, such as 18-22 wt. %.

The hot melt composition according to any of claims 1-5, wherein the synthetic polymer is 70-100% atactic, preferably 90-99.99% atactic, more preferably 95-99.9% atactic, such as 98-99% atactic.

Hot melt composition according to any of claims 1-6, wherein the elastomer is one or more of a copolymer, a block polymer, and a homopolymer, preferably a styrene block polymer.

The hot-melt adhesive composition according to any of claims 1-7, wherein the elastomer is present in an amount of 1-15 wt. %, preferably 2-10 wt. %, more preferably 3-8 wt. %, such as 4-6 wt. %.

The hot melt composition according to any of claims 1-8, wherein the elastomer is one or more of a natural rubber, an artificial rubber, for example a styrene-isoprene-styrene block copolymer, a styrene-butadiene rubber, a styrene-butadiene-styrene block copolymer, a styrene-ethylene-butadiene-styrene block copolymer, a styrene-isoprene-butadiene-styrene block copolymer, a nitrile isoprene rubber, and isoprene-isoprene rubber.

The hot melt composition according to any of claims 1-9, comprising one or more additives selected from: 0.01-10 wt. % was, preferably 1-7 wt. %, such as paraffin, 0.01-50 wt. % resin, preferably 1-30 wt. %, such as a terpene phenol resin, a violin resin, a terpene and a modified terpene, an aliphatic, cycloaliphatic and aromatic resin, a hydrogenated hydrocarbon resin, a tackifying resin emulsion, modified rosin resin, polymerized rosin resin, alpha-pinene resins, β-pinene, terpene resins, terpene phenol resins, alkyl phenol, styrene resins, xylene resins, coumarone resins, indene resins, hydrocarbon resins and combinations thereof, and derivatives thereof, and mixtures thereof, 0.01-5 wt. % filler, preferably 1-2 wt. %, 0.01-5 wt. % plasticizer, preferably 1-2 wt. %, and 0.01-5 wt. % stabilizer, preferably 0.1-1 wt. %.

The hot melt composition according to claim 10, wherein the wax is preferably a high crystalline short chain wax, such as a C 2 -C 5 polymer wax, wherein the melting point of the wax is preferably lower than 100 ° C, more preferably lower than 90 ° C.

Use of a hot-melt adhesive composition according to any one of claims 1 to 11 for obtaining one or more of high initial strength, strong adhesion, low amount, long transferability, and long open time.

Use according to claim 12, in a single-sided or double-sided binding, in particular of binding of large surfaces of 0.5-10 m2, such as 1.5 m2, for example in a foam mattress and furniture.

A product comprising an adhesive composition according to any of claims 1-11.