DD230016A1 - MELT ADHESIVE - Google Patents

Abstract

The invention relates to hot melt pressure sensitive adhesives having low melting temperature and viscosity, high tack and good aging resistance. According to the invention, 20 to 40 wt .-% of an ethylene-vinyl acetate copolymer, 20 to 60 wt .-% of a tackifying resin, in particular of the glycerol ester of rosin, 20 to 60 wt .-% of a low molecular weight, liquid, hydroxyl-terminated polybutadiene and 20 bis 60 wt .-% of a low molecular weight, hydroxyl-terminated, bifunctional poly (alpha-methylstyrene) fused to a homogeneous mass.

Description

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Title of the invention

Hot-melt pressure-sensitive adhesive Field of application of the invention

The invention relates to hotmelt pressure-sensitive adhesives having a low melting temperature, low melt viscosity, improved tack and high resistance to aging »

The hot-melt pressure-sensitive adhesives according to the invention are particularly suitable for those fields of application which require solvent-free and water-free adhesives having a low processing temperature and good flow behavior.

Characteristic of the known technical solutions

Pressure-sensitive adhesives are suitable for many applications if, at normal temperatures, they adhere well and quickly to various substrates, are free from cold flow, withstand shearing stresses and retain the properties during prolonged storage periods.

Particularly important are those pressure-sensitive adhesives which are prepared in the melt without the use of solvents. It is known that ethylene-en-vinyl acetate copolymers are used as thermoplastic base polymers for the production of hot melt adhesives. By combination with tackifiers, plasticizers and optionally polymeric additives such as polyphenylon, amino-formaldehyde resins, polyethylene waxes or polyamides, as well as with fillers, certain properties, such as

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Behavior, the heat resistance and the adhesive force varies or adjusted to a certain degree. The (DD-PS 14? 850) ·

The known systems contain as tackifiers modified or unmodifiziartas rosin, coumarone-indene or poly-styrene resin (DE-OS 19 31 951, DD-PS 60 6O7). Other known tackifiers are terpene or hydrocarbon resins. As plasticizers in particular chlorinated paraffins, polychlorinated polyphenyl, paraffins and other waxes are used (DD-PS 101 178, DD-PS 150 623, DS-PS 1 151 937, DE-OS 1 59A-101, DS-OS 1 524 295) ,

Such hot melt adhesives have a high melting temperature and viscosity in the sail and relatively low tackiness. Sin other part of this hot melt adhesives is the narrow range of application defined by the high processing temperature. Adhesive systems containing rosin or rosin derivatives also have low age, i. Oxidation resistance.

According to DS-OS 2 4-06 618, copolymers of 50 to 90% of alpha-methylstyrene and 50 to 10 % of styrene are also suitable as tackifiers for styrene-butadiene, styrene-isoprene, styiene-vinylacatate copolymers and polychloroprene. The mixtures of resin and polymers are said to give, inter alia, pressure-sensitive adhesives with good tack. In contrast, according to DS-OS 2 348 331 copolymers of alpha-methylstyrene and Vinyltoluen and the fully hydrogenated copolymers of the aforementioned monomers are not effective as a tackifier. In contrast, according to DS-OS 2 348 331, the partially hydrogenated alpha-methylstyrene-vinyltoluene and alpha-methylstyrene-styrene copolymers and partially hydrogenated polystyrene are effective tackifiers. However, only solvent-borne pressure-sensitive adhesives are prepared with these resins, since presumably the melting temperatures and viscosities are also relatively high.

Even hotmelt adhesives with poly (alpha-methylstyrane) according to DS-OS 2 338 258 still have a relatively high melting temperature of 436 K.

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Object of the invention

The aim of the invention is to produce hot-melt pressure-sensitive adhesives having a low melting temperature, low melt viscosity, improved crepitude, good transparency and high resistance to aging.

Explanation of the essence of the invention

It is an object of the present invention to prepare hot melt pressure sensitive adhesives by developing adhesive mixtures which satisfy the above requirements.

Slide task is inventively achieved in that

a) 20 to 40% by weight of an ethylene-vinyl acetate copolymer containing from 20 to 45% by weight of vinyl acetate units,

b) 20 to 60 wt. -JF ₀ of a tackifying resin, particularly rosin, coumarone-indene resins, terpene, or hydrocarbon resin, preferably of the Glycerinesters of rosin

c) 20 to 60 uew .- $ of a low molecular weight, liquid, hydroxyl-terminated polybutadiene

and

d) 20 to 60% by weight of a low molecular weight, bifunctional, hydroxyl-terminated polyalkyl-methylstyrene)

be merged with each other.

The liquid, hydroxyl-terminated polybutadienes have an average molecular weight Mn of 1000 to 5000, a microstructure of 10 to 90 fo 1,2- or 90 to 10 % 1,4-3utadisneinheiten and a hydroxyl content of 0.5 to 3.4 Ground $.

The low molecular weight, hydroxyl-terminated poly (alpha-methylstyrsne) have an average molecular weight Mn of 500 to 800 and contain 1.5 to 2 hydroxyl end groups per molecule.

The order of blending the four components is not critical to the adhesive blends of the present invention.

The adhesive composition is usually hairy in one

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Stirred kettle at about 4-13 K melted. The batch is mixed until a clear, homogeneous composition has formed.

The melting temperature of the hot melt pressure sensitive adhesive is 383 to 4-13 K, the melt viscosity about 500 to 3000 mPa.s.

The addition of the liquid polybutadiene and of the low molecular weight hydroxyl-terminated poly (alpha-methylstyrene) lowers the melting temperature and viscosity compared to known adhesive mixtures of ethylene-vinyl acetate copolymer, rosin and known plasticizers and improves tack and oxidation resistance.

Exemplary embodiments Example 1

20 parts by mass of a glycerol ester of rosin are placed in a heated mixing vessel with stirring and melted after the complete melting of the glycerol werderi 20 parts by weight of the vinyl-vinyl acetate copolymers were added, which can also be completely melted. Finally, 30 parts by mass of a low molecular weight, liquid, hydroxyl-terminated polybutadiene and 30 parts by weight of a low molecular weight, b! Functional, hydroxyl-terminated poly (alpha-methylstyrene) are added to the melt and the melt is stirred until complete homogeneity. The melting temperature of the obtained hot-melt pressure sensitive adhesive is 408 K and the melt viscosity is 2000 mPa.s.

Example 2

The Arbeitswaise of Example 1 is repeated, wherein 20 parts by weight of the Glycerinestars of rosin, 20 parts by weight of the ethylene-vinyl acetate copolymer, 20 parts by weight of the low molecular weight, liquid hydroxyl-polybutadienes and 4O Hasseteile the low molecular weight, b! Functional hydrozylterminiarten poly (alpha-methyl styrens) are used. The melting temperature of the obtained hot-melt pressure sensitive adhesive is 4-03 K and the melt viscosity is 2000 mPa.s.

Claims (2)

Claim for invention Hot-melt pressure-sensitive adhesive based on ethylene-vinylacatate copolymers and tackifying resins, characterized in that the adhesive composition comprises a) from 20 to 40% by weight of a vinyl-vinyl acetate copolymer containing from 20 to 45% by weight of vinyl acetate, b) 20 to βθ wt-fS the glycerol ester of rosin c) 20 to βθ wt .- ^ a low molecular weight, liquid, hydroxyltarrainiarten polybutadiene having an average molecular weight Mn of 1000 to 5000, a micr © structure of 10 to 90 <fo 1,2- or 90 to 10% 1,4 Butadiene units and a hydroxylgahalt of 0.5 to 3.4 mass and d) 20 to βθ Gaw. ~ £ of a low molecular weight, hydroxyl-terminated polyalkyl-ethylstyrone), the 1.5 to Contains 2 hydroxyl end groups per molecule and has an average molar mass Mn of 500 to 800, consists.