Packaging adhesive tapes

0001The invention relates to the development of pressure sensitive adhesive tapes based on Butadiene / methyl methacrylate latexes with a high butadiene content and Resin dispersions.

0002In the patent literature a variety of applications for manufacturing exists Packaging tapes.

0003The long-known classical Klebemassesyteme for packing tapes are essentially based on natural rubber, styrene block copolymers and polyacrylates.

0004The natural rubber systems are usually as a solution in an aliphatic used solvent mixture. Water-based natural rubber compounds based latex centrifuges are also known. To set the required adhesive properties is the addition of resins, fillers, anti-aging agents unavoidable. Crosslinking takes place either chemically about added crosslinking agents, or physically via eg electron.

0005Synthetic rubbers based on styrene block copolymers were in the Past also described as adhesives for packaging tapes. This is SiCN by 100% systems which after mixing with resins and other coagents in the molten state without the presence of Solvents or water can be applied.

0006Use of polyacrylates as adhesive compositions for adhesive packaging tapes is also known. In addition to solutions of polyacrylates are in the past polyacrylate also been described, according to the compounding with resin dispersions and further coagents the requirements of a packaging tape measures fulfill. Acrylate dispersions show a relatively poor To the touch to cartons, particularly when the substrate is made repeatedly recycled papers comes what in packaging cartons are increasingly the case is. By adding resin dispersions this deficiency can be eliminated will. As natural resin dispersions based on rosin derivatives which often affect cohesion of acrylate undesirably operated you are more likely the more cohesive hydrocarbon resin dispersions of various resin manufacturers offered.

0007Backing materials used for packaging tapes are usually mono- or biaxially oriented polyolefins, PVC grades or papers used.

0008Butadiene / styrene latexes are in the range of "Pressure Sensitive Adhesives" since many years used for impregnating and stabilizing backing materials. Here are papers woven and nonwoven fabrics in the foreground. The impregnation or coating must not be sticky due to the application. The butadiene used for this application / styrene copolymers have therefore contain a relatively high proportion of hardening monomers, but On the other hand enough softening monomer, so that the copolymer a whole is still elastic. Butadiene / styrene latices with a butadiene content of about 25-50% meet this requirement very well. Films of these copolymers are moderately elastic depending on the butadiene content to elastic, and not adhesive. Such copolymers are for many years on the Commodity market available (BUTOFAN® types of BASF, various types of Dow and Synthomer). Due to their preparation containing such latexes or Dispersions emulsifier systems to provide a compatibility between the organic and the aqueous phase to produce.

0009Butadiene / styrene copolymers were in the past, as base polymers used for label materials. In the field of labels cohesion comes often secondary to meaning, so that weakly adhering systems by compounding with usual Tackyfiern in many cases sufficient properties show.

0010As backbone polymer for packaging tape compositions are not or weakly adhesive copolymers based on butadiene / styrene copolymers poorly suitable because they made only with substantial amounts of sticky Tackyfierharzen can be, in turn, connected to a far-reaching loss of cohesion is. This includes use as an adhesive for packaging tapes out.

0011Butadiene / styrene copolymers with a high butadiene content, however, are as Framework polymers for packaging adhesive tapes of high interest.

0012Butadiene copolymers, as copolymerisation a hard and thus containing cohesive segment, are as framework polymers for demanding but PSAs of grundsätzlichlichem interest.

0013The object of the invention was further butadiene copolymers for the described to provide application that does not have the aforementioned shortcomings, and with where a pressure sensitive adhesive tape can be made that one of the requirements is packaging tape justice.

0014The object is achieved by the use of butadiene / methyl methacrylate Dispersions having a high butadiene content, with suitable Resin dispersions were mixed. Among the compounds thus obtained may optionally further coagents such. as anti-aging agents or other emulsifiers are admixed to improve the anti-aging or Unrolling further adapt to the application. After coating the Adhesive on a polymer or paper base is a pressure sensitive adhesive tape available, the the requirements of an adhesive packaging tape with respect to tack, Adhesive strength, cohesion and unrolling fully met.

<u>Adhesives:</u>

0015The copolymerization of methyl methacrylate with butadiene in an aqueous medium provides copolymers which are film-forming, and the one for pressure-sensitive exhibit gluing appropriate Tg. Butadiene / Metylmethacrylat dispersions generally stabilized by incorporating small amounts of carboxyl groups, same thing adhesion to many substrates improved.

0016Adhesive compositions of the invention may in particular carboxylated Butadiene / methyl methacrylate copolymer dispersions are used with a Butadiene portion of 55-95%, preferably 60-85%, based on the Total solids content of methyl methacrylate and butadiene, with a mixture Resin dispersions a hevorragende suitability as adhesives for Show packaging tapes. contain such copolymers Carboxylated especially below 10%, preferably below 5% based on the monomer content carboxyl comonomer, especially acrylic acid in the copolymer.

0017Inventive butadiene / methyl methacrylate dispersion types with a one Butadiene content> 60% are as Synthomer available.

0018As the resin component can both dispersions of synthetic resins (eg Hydrocarbon resin, terpene-phenolic resins, etc.), as well as natural resin dispersions (Z. B. rosin derivatives, polyterpenes, etc.) are used.

0019Hydrocarbon resin dispersions are due to the high cohesion clearly prefer. The melting point of the base resin should be in the range 50-120 ° C, preferably 60-100 ° C. Based on the total solids content Butadiene / methyl methacrylate copolymer resin and the resin should share in the range 5-60%, preferably 10-40% lie. For the targeted setting of the adhesive Properties, mixtures of different resins also used will. To improve the aging behavior dispersions usual Anti-aging agents are added which in the field of elastomers are well known.

0020Furthermore, other additives to adjust the product properties when required be added, such as fillers, plasticizer resins, oils or emulsifiers eg the type of alkoxylated alkylphenols. With these additives, it is possible the unwind to influence in the desired manner.

0021The adjustment of adhesion / cohesion balance may by chemical crosslinking on the carboxyl groups present by means of added crosslinking agents such as aluminum or titanium chelate done. A radiation crosslinking is in contrast to many styrene block copolymer due to the sufficient high molecular weight also possible.

0022An overview of possible resin dispersions can be found in: Donatas Sata,<i>Handbook of Pressure Sensitive Adhesive Technology,</i> 2. Edition Resin Dispersion by Anne Z. Casey S. 545-566

0023Inventive resin dispersions such as are available from Hercules (NL).

0024The adhesive coat weight is 10-120g / m², Preferably 15-40g / m²,

<u>Support materials:</u>

0025Backing materials used for the invention, for packaging applications come conventional carrier materials. This is to substantially Films and papers or because of their properties and the manufacturing Treatment process, the required mechanical properties.

0026In the case of the films is substantially polyethylene, polypropylene, Polyvinyl chloride and other customary for the application of polymers and copolymers, which can be used either a single-layer or multilayer. In multi-layer systems is also the composition and the thickness of the individual layers vary.

0027Monoaxially and biaxially oriented polypropylenes are widely used for packaging tapes, Strapping tapes, and other adhesive tapes used in which a defined tenacity of considerable importance.

0028Monoaxially oriented polypropylenes exhibit particularly good tensile strength and low elongation in the longitudinal direction. Such support materials are widely used for Strapping applications.

0029To achieve uniform strength values ​​in longitudinal and transverse directions must Films are biaxially stretched.

0030Both mono- biaxially oriented polypropylene and polyethylene are as Support material for the invention particularly suitable. orient the stretching ratios thereby. to the corresponding requirements

0031Both wind, and flat film may be used.

0032The thicknesses of the films are from 10 to 250 .mu.m, preferably between 20 and 120 microns.

0033To ensure sufficient adhesion of the adhesive on the carrier material ensure has the surface energy of the side to be coated within a defined range are. This can either be via an additional Coating be ensured with a primer or a surface treatment. Preferably, a corona or flame pretreatment, with the can be achieved the desired surface energies. The surface energies should be in a range of 25-50mN / m, preferably 30-45 mN / m lie.

0034As support materials, besides coming impregnated and highly sized defined creped papers with tear strengths into consideration, the desired the meet requirements. Depending on the desired application, both papers with greater machine direction stretchability is used as cross-elasticity are, as well as papers with greater cross direction stretchability than machine direction stretchability, both in bleached, as well as in environmentally friendly unbleached version.

0035All percentages refer to% by weight.

<u>Examples:</u>

example 1

0036A dispersion adhesive composition consisting of 70% of a carboxylated Butadiene / methyl methacrylate dispersion having a butadiene content of about 70% (VL 10533, butadiene / methyl methacrylate dispersion Synthomer) and 30% Tacolyn 1070 (KW-resin dispersion from Hercules) is with a wire bar continuously with a layer thickness of 25 g / m² on a 35 mN / m corona treated 30 micron thick BOPP film coated. Percentages are based on the solids content.

<u>Technical conditions</u>

:

0037<tables><table><tgroup cols="2"><tbody><row><entry align="left">machine</entry><entry align="left">Pilot coating plant</entry></row><row><entry align="left">commissioned</entry><entry align="left">wire bar</entry></row><row><entry align="left">Support web speed</entry><entry align="left">3.5 m / min</entry></row></tbody></tgroup></table></tables>

0038The coated material is subsequently dried thermally:<dl tsize="33" compact="compact"><dt>Drying (suspension nozzle dryer):</dt><dd>Zone 1: 80 ° C Zone 2: 85 ° C</dd></dl>

0039The ball material is then cut into rolls.

<b>Adhesive Data (fresh state)</b>

:

0040<sl><li>Adhesion / steel: 2,20N / cm</li><li>Microscherweg (40 ° C, 3N: 10 microns</li><li>Thermoscherweg (5 ° C / min, 3N): 150 ° C</li></sl>

<b>Example 2:</b>

0041A dispersion adhesive composition consisting of 80% of a carboxylated Butadiene / methyl methacrylate dispersion having a butadiene content of 70% (VL 10511, butadiene / methyl methacrylate dispersion Synthomer) and 20% Tacolyn 1070 (KW-resin dispersion from Hercules) is with a wire bar continuously with a layer thickness of 25 g / m² on a 35 mN / m corona treated 30 micron thick BOPP film coated. Percentages are based on the solids content.

<u>Technical conditions</u>

:

0042<tables><table><tgroup cols="2"><tbody><row><entry align="left">machine</entry><entry align="left">Pilot coating plant</entry></row><row><entry align="left">commissioned</entry><entry align="left">wire bar</entry></row><row><entry align="left">Support web speed</entry><entry align="left">3.5 m / min</entry></row></tbody></tgroup></table></tables>

0043The coated material is subsequently dried thermally:<dl tsize="33" compact="compact"><dt>Drying (suspension nozzle dryer):</dt><dd>Zone 1: 80 ° C Zone 2: 85 ° C</dd></dl>

0044The ball material is then cut into rolls.

<u>Adhesive Data (fresh state):</u>

0045<sl><li>Adhesion / steel: 2,40N / cm</li><li>Microscherweg (40 ° C, 3N: 156 pm</li><li>Thermoscherweg (5 ° C / min, 3N,): 58 ° C</li></sl>