DD230014A1 - 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, 40 to 60 wt .-% of a tackifying resin, in particular the glycerol ester of rosin, and 20 to 40 wt .-% of a low molecular weight, hydroxyl-terminated hydroxylated polybutadiene to a homogeneous Mass merged.

Description

Title of the invention; Hotmelt PSA Field of application of the invention;

The invention relates to hotmelt pressure-sensitive adhesives having a low melting temperature, low melt viscosity and improved tackiness.

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 Y working temperature and good flow behavior. ¹

Characteristic of the known technical solutions

Pressure-sensitive adhesives are suitable for many applications if they stick well and quickly to various substrates at hormaltemperature, are free from cold flow, withstand shear stresses and retain these properties during prolonged storage periods. Of particular importance are those pressure-sensitive adhesives which are prepared in the melt without the use of solvents.

It is known that ethylene-vinyl acetate copolymers (E7A) are used as thermoplastic base polymers for the production of hot melt adhesives. By combination with tackifiers, plasticizers and, where appropriate, poly-

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In addition to other additives, such as polyphenyle η, amino-formaldehyde resins, polyethylene waxes or polyamides, as well as PUllstoffen certain properties, such as flow, heat resistance and adhesive strength can be varied or adjusted to a certain extent targeted (DD-PS 147 850).

.The known systems contain as tackifying substances modified or unmodified rosin, coumarone-indene or polystyrene resin (DE-OS 1 931 951, DD-PS 60 607). Other known tackifiers are terpene or hydrocarbon resins. ' The plasticizers used are in particular chlorinated paraffins, polychlorinated polyphenyl, paraffins and other waxes (DD-PS 101 178, DD-PS 150 623, DE-PS 1 151 937, DE-OS 1 594 101, DE-OS 1 524 295). '

Such hot melt adhesives generally have a high melting temperature and viscosity and relatively low tackiness. ' Another disadvantage of these hotmelt adhesives is the narrow range of application defined by the high Y working temperature. Adhesive off systems, the rosin or ' Rosin derivatives also have a low aging, d.'h. ' Oxidation resistance. '

Aim of the invention

The aim of the invention is to produce hotmelt PSAs having a low melting temperature, low melt viscosity, high tack, good transparency and resistance to aging.

Explanation of the essence of the invention

The invention has for its object to produce hot melt pressure sensitive adhesive by developing adhesive mixtures that meet the above requirements «'

The object is achieved in that

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

b) 40 to 60 wt .-% of a tackifying resin and

c) 20 to 40 gevi, '-% of a low molecular weight, liquid, hydroxy-terminated polybutadiene

be merged with each other. '

The ethylene-vinyl acetate copolymers may contain 20 to 45 units of isocyanate acetate. '

The tackifying resins themselves are known, for example rosin, coumarone-indene, terpene or hydrocarbon resins. Preferably, the glycerol ester of rosin is used.

The liquid, hydroxyl-terminated polybutadienes have an average molecular weight lh of 1,000 to 5,000, a macrostructure of 10 to 90 % 1,2 or '90 to 10 % 1,4-butadiene units and a hydroxyl content of 0.5 to 3 , 4 measures -fo . '

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

The adhesive composition is usually in a heated stirred tank at about ' 408 K melted. ¹ The mixture is mixed until a clear, homogeneous composition has formed «

The melting temperature of the hot melt pressure sensitive adhesive is 398 to 408 K, the melt viscosity 500 to 3,000 mPa.'S. By adding the liquid polybutadiene, the oxidation resistance and the tackiness over known adhesive mixtures of ethylene-ynyl aaetate copolymers, rosin derivatives and known plasticizers are improved and the melting temperature and viscosity are lowered.

Embodiments Example 1

After complete melting of the glycerol ester of rosin 30 parts by weight of the ethylene-vinyl acetate copolymers are added, which can also be completely melted · Finally, the melt 40 liasseteile one low molecular weight, liquid hydrosylterminierten polybutadiene added and the melt stirred until complete homogeneity · ¹

Example 2

The procedure of Example 1 is repeated, with 40 parts by mass of a glycerol ester of rosin, 20 parts by mass of the ethylene-vinyl acetate copolymer and 40 parts by mass of the low molecular weight, liquid hydroxy! Terminated polybutadiene are used.

Example 3

The procedure of Example 1 is repeated, wherein 45 parts by weight of a glycerol ester of rosin, 25 parts by weight of ethylene vinyl acetate copolymers η and 30 parts by weight of the low molecular weight, liquid hydroxyl-terminated polybutadiene are used.

Claims (1)

I2rf training request. Adhesive pressure-sensitive adhesives based on ethylene-vinyl acetate copolymers and tackifying resins, characterized in that the adhesive mixture comprises a) from 20 to 40% by weight of an ethylene-vinyl acetate copolymer containing from 20 to 45% by weight of vinyl acetate, b) 40 to 60 wt .-% of the glycerol ester of rosin and c) 20 to 40 parts by weight 55 of a low molecular weight, liquid hydroxy-terminated polybutadiene having an average molecular weight Sn of from 1,000 to 5,000, a microstructure of from 10 to 90 % 1,2- or ' 90 to 10 % of 1,4-butadiene units and one Eey droxy Ige has from 0.5 to 3.4 l, consists.'