Stock material or miscellaneous articles – Surface property or characteristic of web – sheet or block
Reexamination Certificate
1999-12-09
2001-12-18
Pyon, Harold (Department: 1772)
Stock material or miscellaneous articles
Surface property or characteristic of web, sheet or block
C428S474400, C428S480000, C524S230000, C524S492000, C524S493000
Reexamination Certificate
active
06331355
ABSTRACT:
This invention provides a monolayered thermoplastic hot-melt adhesive film made from thermoplastic copolyamides and/or copolyesters which is modified by the addition of additives in such a way that it can be prepared without an additional separating layer, does not block on the reel and nevertheless retains its ability to hot- bond, as a property which is required for its application according to the invention, such as two-dimensional fixing or bonding of other substrates.
Plastics films are known in many variants and for many applications. One particular embodiment is hot-melt adhesives or hot-melt films, which are understood to be films made from thermoplastic plastics which are suitable, in the molten state, for bonding other substrates due to the surface tackiness and flow properties which are then present and to their thickness. The properties and advantages of hot-melt adhesive films and methods for their preparation from current hot-melt adhesive granules or powders are described, for example, in U.S. Pat. No. 4,379,117 or DE 2 114 065. The use of hot-melt adhesive films is explained by way of example in DE 3 911 613. A general categorisation of adhesives can be found, for example, in G. Habenicht; Kleben: Grundlagen, Technologie, Anwendungen, Springer Verlag, Berlin, 1986.
The low softening or melting points of these hot-melt adhesive films or hot-melt films means that the films block on the reel. Furthermore, these materials have the disadvantage that they have very smooth surfaces which thus contribute to the blocking characteristics of the films. This impairs the running properties of machines handling them. Therefore the films have to be guided permanently by moveable parts or strips of separating material in order to prevent bonding to stationary parts and thus interrupting the process.
The prior art for processing these blocking materials to give monolayered strips is the use of separating layers such as, for example, are mentioned in DE 2 114 065. Separating layers consist, for example, of fabrics, films or siliconised papers.
The disadvantage of separating layers is that they themselves have to be produced, which leads to an increase in the cost of the hot-melt adhesive films produced. In addition, they are mostly undesirable because the separating layers have to be rolled up separately and often have to be disposed of as waste. Since these separating layers can never be fully recycled, they represent both a financial and ecological burden.
An alternative to the use of separating layers is to provide tacky or blocking materials with lubricating or antiblocking agents such as, for example, described by Botz in Taschenbuch der Kunststoff-Additive, Gachter, Muiller (eds.), 2nd. edition, Hanser Verlag, Munich, 1983, p. 229-274, of the type which are known to prevent blocking on the reel and produce a lubricating effect on machines. The adhesive properties of the films are modified by the use of such materials. The disadvantage of systems disclosed hitherto is that they modify the adhesiveness or sealability of the material or strength of the seal produced, due to coating the surface, in such a manner that they do not achieve the initial level of materials which have not been treated as a result of having to adjust the process parameters such as pressure, temperature and time.
A generally widespread procedure is also the integration of tacky and blocking materials into multi-layered structures in which the various layers only bond in the warm and do not block against each other in the cold. Thus, U.S. Pat. No. 4 629 657, EP 0 424 761 or EP 0 263 882 describe polyolefin films which are coated with hot-sealable materials. In this case, the less tacky layer takes on the function of a separating layer. These films have the disadvantages that they have only one hot-sealable face, also the bond adhesion which can be achieved is low and the end product has a not inconsiderable tendency to roll.
Therefore there is the object of providing a monolayered film with high adhesive power for heat laminating, sealing and fixing which can be rolled up and unrolled without adhering to itself and can be passed through current processing machines with a low likelihood of blocking.
According to the invention, it is possible to provide a monolayered hot-melt adhesive film made from copolyesters and/or copolyamides which has no separating layer and which adequately satisfies the requirements mentioned, which is characterised in that it can be rolled up and unrolled without adhering and without the additional use of a separating layer and the polymer matrix of copolyamide and/or copolyester contains an additive combination of 0.4 wt. % to 8.0 wt. % of a spacer and 0.05 wt. % to 1.0 wt. % of a separating and lubricating agent, and optionally up to 1 wt. % of other additives, each with respect to the total mixture.
In a preferred embodiment, an additive combination is used which is characterised in that it contains 0.4 wt. % to 8.0 wt. % of a silica and 0.05 wt. % to 1.0 wt. % of a long-chain and/or cyclic fatty acid amide.
In a particularly preferred embodiment, an additive combination is used which is characterised in that it contains, in addition to the specified long-chain and/or cyclic fatty acid amide, 0.02 wt. % to 0.4 wt. % of a soap as a separating and lubricating agent.
In a preferred embodiment, the additives are incorporated into the polymer matrix of copolyesters and/or copolyamides by means of a masterbatch, characterised in that the additive batch is built up from 35 wt. % to 80 wt. % of copolyester and/or copolyamide, 20 wt. % to 50 wt. % of silica, 2 wt. % to 10 wt. % of a long-chain and/or cyclic fatty acid amide and 0.5 wt. % to 5 wt. % of soap.
Suitable starting materials for the polymer matrix are the corresponding thermoplastic hot-melt adhesives which are currently available on the market from known suppliers and are available, for example, under the commercial names Dynapol®, Vestamelt®, Platamid®, Bostik and Griltex®. The adhesive raw materials used according to the invention are preferably thermoplastic copolyamides and/or copolyesters.
The viscosity of polymer matrix materials is generally characterised by the melt flow index (NMFI) and the melt viscosity. The melt flow indices of the polymer matrix components are preferably between 1.5 g/10 min and 150 g/10 min, measured according to DIN 5 37 35 at 160° C. and with a test weight of 2.16 kg. The melt viscosities of the polymer matrix materials are preferably between 400 Pa.s and 1000 Pa.s, measured according to ISO 1133 at a temperature of 160° C.
Furthermore, hot-melt adhesive raw materials which have a thermoanalytically determined maximum main melting point of between 80° C. and 130° C. are preferred.
Suitable spacers are natural silicas, synthetic silicas and polymeric spacers. Natural silicas are preferably used. Fats, waxes and soaps are suitable as separating and lubricating agents. Long-chain and/or cyclic fatty acid amides which contain aliphatic groups with a carbon chain length of preferably 14 to 20 carbon atoms are preferably used. Suitable third additive components are soaps with a chain length of 12 to 20 carbon atoms. In a preferred form, these soaps are preferably present as the calcium salt.
Due to the use of the additive combination according to the invention, it is possible to prepare hot-melt adhesive films which not only have good machine-running properties, but also do not require the otherwise conventional separating layers which, as is known, increase the manufacturing costs of the films to a not inconsiderable extent. To a person skilled in the art, who has received the relevant training and experience, it would not be obvious that the antiblocking/separating agent combination according to the invention would not have a long-lasting negative effect on the adhesive properties of the mixture/film formulations according to the invention.
Normal thermal forming processes for processing plastics are suitable for preparing hot-melt adhesive films according to the invention. In particular, melt
Schledjewski Ralf
Schultze Dirk
Tebbe Heiko
Franks James R.
Gil Joseph C.
Preis Aron
Pyon Harold
Tsoy Elena
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