Adhesive tape particularly for wrapping purposes
Abstract
Adhesive tape with self-adhesive finish on one side, consisting of a. a stretch-oriented polyolefin sheet, with the face of the sheet farthest from the adhesive layer, free of any surface treatment, b. layer of adhesive applied to the sheet on one side, prepared from a mixture containing 30 to 65% by weight of natural rubber latex 35 to 70% by weight of an aqueous dispersion of resins from hydrocarbon resins, where it is used as dispersion of resins, a dispersion of C5 / C9 hydrocarbons, modified with aromatics.
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9 claims: 8 independent, 1 dependent
- 1ES 2 256 286 T3 REIVINDICACIONES 1. Cinta adhesiva con acabado autoadhesivo por uno de sus lados, consistente en a. una lámina de poliolefina orientada por estiramiento, con la cara de la lámina más alejada de la capa de adhesivo, exenta de cualquier tratamiento superficial, b. capa de adhesivo aplicada sobre la lámina por uno de sus lados, preparada a partir de una mezcla conteniendo 30 a 65% en peso de látex de caucho natural 35 a 70% en peso de una dispersión acuosa de resinas a partir de resinas de hidrocarburo, en donde se emplea como dispersión de resinas, una dispersión de hidrocarburos C5/C9, modificada con aromáticos.
- 2Cinta según la reivindicación 1, caracterizada porque, la lámina es de poliolefina orientada por estiramiento, presentando un espesor entre 20 y 50 jum.
- 3Cinta según la reivindicación 1 y 2, caracterizada porque, la lámina consiste en una lámina de polipropileno estirada monoaxialmente que presenta un espesor entre 25 y 200 jum, prefiriéndose en cualquier caso las de 40 y 130 μm de espesor.
- 4Cinta, como mínimo según una de las reivindicaciones precedentes, caracterizada porque, se ha aplicado una capa de imprimación entre la lámina y la capa de adhesivo.
- 5Cinta, como mínimo según, una de las reivindicaciones precedentes, caracterizada porque, la dosificación para la capa de adhesivo aplicada sobre la lámina es de 10 a 45 g/m 2 .
- 6Cinta, como mínimo según una de las anteriores reivindicaciones, caracterizada porque, la capa de adhesivo contiene un 20% en peso de, como mínimo, una resina en dispersión a base de resinas de hidrocarburos que presenta un punto de reblandecimiento entre 20 y 85°C.
- 7Cinta, como mínimo según una de las anteriores reivindicaciones, caracterizada porque, la capa de producto adhesivo contiene De 0,1 a 5% en peso de un agente inhibidos del envejecimiento. De 0,5 a 4% en peso especialmente de 0,3 a 3% en peso de un alquilfenol alcoxilado. De 0,5 a 5% en peso de un antiespumante y/o De 0,05 a 20% en peso de, cómo mínimo, un pigmento colorante
- 8Cinta, como mínimo según una de las anteriores reivindicaciones, caracterizada porque, al desenrollar la cinta adhesiva emite un volumen de ruido inferior a 80 dB (A) determinado a una distancia de 25 cm desde el centro del rollo de cinta adhesiva y a una velocidad de desenrollado de 45 m/min.
- 9Utilización de una cinta según cualquiera de las reivindicaciones de 1 a 7 a modo de cinta adhesiva para embalajes que ofrece una buena capacidad de agarre con respecto al cartón, especialmente cuando éste es reciclado, una cohesión adecuada, un buen nivel de seguridad para el artículo embalado, un buen anclaje del adhesivo y facilidad para su desenrollado.
Independent claims9
182 paragraphs in 10 sections, as filed
IS 2 256 286 T3
DESCRIPTION
Special adhesive tape for packaging.
The invention relates to an adhesive tape provided with a polyolefin-based support, which is covered on one side with a solvent-free adhesive mass, made from natural rubber latex, as well as to the application of the tape as adhesive tape for packaging.
Adhesive tapes made from polyolefin films, such as biaxially stretched polypropylene, and adhesives made from natural rubber with solvents or aqueous acrylate dispersions, are known and distributed by well-known manufacturers.
A description of these products can be found for example in “Packaging Tapes” by Stefan Rober in the Pressure Sensitive Adhesives Technology Manual, third edition, edited by Donatas Salas, Salas & Associates, Warwick, Rhode Island pp. 787-814. Other references can be found in "European Adhesives & Sealants" 10 (4), 1993, 29 by G. Pedala and in "European Adhesives & Sealants 2 (2), 1985, 18 by RW Andrew"
Taking into account the known disadvantages derived from the manufacture of adhesive tapes that contain solvents such as, for example, the costly recycling of solvent products, the emission of solvent products into the environment, the risks in the workplace derived from the products easily flammable solvents and the limitation of the coating speed due to the drying of the adhesive mass, they make the technologies for the manufacture of adhesive tapes free of solvent products acquire a priority importance.
Apart from the already described problem of the technology of solvent products, there is another negative aspect such as the necessary unfolding of the natural rubber for the elaboration of the adhesive masses, this is chewing. This results in a clear reduction in the cohesion force of the adhesive according to the intensity of the disintegration caused by the applied mechanical load.
The technical process to be carried out aimed at the objective of the disintegration of the rubber under the combined effect of the shear stress, the temperature and the oxygen of the air, is designated in the technical literature as mastication (from the English: mastication) and almost always carried out in the presence of chemical auxiliary products, which in the technical literature are known as chewing or peptizing agents, even sometimes also known as "chemical plasticizers".
The chewing operation is necessary in rubber technology, in order to facilitate the admission of additives.
According to Rompp (Rompp Lexikon Chemie - Version 1.5, Stuttgar / New York: Editorial Georg Thieme 1998) chewing is defined according to the technological terminology of rubber as the decomposition of the long chain molecules of rubber to increase plasticity and at the same time reduce of the viscosity (Mooney-) of the rubbers. Chewing is carried out by special treatment of the rubber in kneaders or between rollers, if possible at low temperatures in the presence of auxiliary products for chewing (chewing). The powerful mechanical forces that act there lead to the "tearing" of the rubber molecules, giving rise to macro-radicals whose recombination by reaction with the oxygen in the air is prevented. Auxiliary chewing agents such as aromatic or heterocyclic mercaptans as well as their zinc or disulfide salts accelerate the chewing process by promoting the creation of primary radicals. Activators such as metals (iron-, copper-, cobalt-) salts of tetraazaporphyrins or Phthalocyanines facilitate the reduction of the chewing temperature. Auxiliary agents for chewing are used for chewing natural rubber in amounts of approximately 0.1 to 0.5% by weight in the form of masterbatch, to facilitate a uniform distribution of these minimal amounts of chemicals used in rubber mixtures. .
Mastication is difficult to differentiate from all the usual solvent-free polymer technologies, which results in disintegration, degradation (English: degradation) that occurs in the melt, as happens in the preparation of compounds, in the transfer and when making coatings.
Degradation is a collective designation for different processes, in which the appearance and characteristics of plastic materials are modified. Degradation, for example, can be caused by chemical, thermal, oxidative, mechanical or biological effects as well as by the effect of radiation such as ultraviolet light. In this case, the consequences are, for example, oxidation, chain separation, depolymerization, crosslinking as well as the separation of polymer side groups. The stability of the polymers against degradation can be increased by using additives, for example with the addition of stabilizers such as antioxidants or light stabilizers.
The use of highly peptonized adhesives made from natural rubber hot-melt adhesives for adhesive tapes, especially packaging adhesive tapes, intended to close cardboard boxes made from recycled paper or cardboard, are the cause of the boxes opening ahead of schedule. With a considerable closing tension of the cardboard box due to the pressure exerted by the filling material
ES 2 256 286 T3 packed in the same or by the closing tension contrary to that effected by the packed material, the adhesive tape detaches from the surface of the box and the latter opens as the adhesive tape of the packaging slides.
Adhesive tapes for packaging, intended for boxes, cannot be made from natural rubber applied as an adhesive coating mass, using nozzles. The cohesion of this type of masses is not enough.
The cohesion and thus the safety of the packaging offered by the adhesive tapes made with adhesive masses from natural rubber, can be improved by crosslinking the rubber adhesive mass and / or by varying the manufacturing process of the adhesive mass, in order to what the natural rubber used, it has to undergo a less intense unfolding and therefore offer a higher molecular weight. In this way, the sliding of the adhesive tape on the surface of the cardboard can be counteracted, as previously described.
Technologies in which no solvents are used for the manufacture of adhesive tapes, especially in adhesive tapes for packaging, have hitherto been limited to the use of adhesive masses made from acrylate dispersions as well as to the application of thermoplastic elastomers. fuses.
The advantage offered by these thermoplastic elastomers, which are predominantly block-blocked copolymers of polystyrene, is their relatively low softening point and the ease of application associated with them including the process for brushing and the possibility of avoiding the previously described disadvantages that present the technologies based on solvent products.
Other solvent-free systems based on water-based adhesives, such as adhesive systems made from polyvinyl acetate, polyvinyl acetate-ethylene copolymers, neoprene, styrene-butadiene, polyurethane, polyvinyl alcohol, have no or only very little application due to the lack of cost savings and / or performance for adhesive tapes, especially if they are intended for the manufacture of adhesive tapes for packaging.
A summary of the most important water-based adhesive systems as well as their application can be found in “Solvent free adhesives”, TE Rolando (HB Fuller) in Rapra Rev. Rep. 1997, 9 ( 5), 3-30 Rapra Technology Ltd.
Hitherto, different methods for the manufacture and application of solvent-free rubber adhesives have been disclosed.
A summary of such adhesives and their use in the field of Pressure Sensitive Adhesives can be found in "Natural Rubber Adhesives" (GL Butler in the Pressure Sensitive Adhesive Technology manual). , third edition, edited by Donata Satas, Van Nostrabd Reinhold New York, pp. 261-287).
All known processes are distinguished by their considerably strong rubber splitting. In the subsequent handling of the masses for self-adhesive tapes, this requires extreme crosslinking conditions, also partially restricting the application profile, consequently and especially for the use of self-adhesive tapes suitable for high temperatures. Solvent-free hot melt adhesives made from non-thermoplastic elastomers, such as natural rubber or other high molecular weight rubbers, have insufficient cohesion for most applications without the crosslinking step of the adhesive mass. not being indicated to be applied in the field of adhesive tapes for packaging. The reason for this failure of non-crosslinked adhesives made from natural rubber is the relatively considerable reduction in molecular weight through transformation, as well as due to the process of making the adhesives from natural rubber and the resulting decrease and insufficient cohesion of the adhesive masses, due to this.
CA 698 518 describes a process for obtaining a dough by adding a high percentage of plasticizer and / or at the same time vigorously chewing the rubber. Certainly, according to this method, adhesives with extremely high adhesive strength, with a relatively high percentage of plasticizer or also with the strong disintegration of the molecular structure of the elastomer can be achieved up to an average molecular weight of Mw <1 million, which can only be achieved with limitations. shear strength required by users, including high crosslinking.
The use of polymer blends, in which, apart from non-thermoplastic natural rubber, block copolymers are also used in a proportion of approx. of 1: 1, an unsatisfactory compromise solution is essentially established that neither provides shear strengths for the use of the self-adhesive tapes required for high temperature applications, nor does it provide any considerable improvement over the properties described in CA 698 518.
Virgin natural rubber latex is supplied from plantations, proceeding to its cleaning, conservation and concentration, following appropriate methods. In general latex types and methods for transformation are described in the publication "Naturkautschuk" - "Technisches Infomationsblatt" Malaysian Rubber Producers Research Association, L1, 1977 and in "Kaustschuktechnologie", Werner Hofmann, Publishing Gentner Stuttgart S. 51ff.
IS 2 256 286 T3
Natural rubber latex is collected as a natural product from so-called rubber trees. After various work processes for separation and cleaning, four basic types of latex from natural rubber are distinguished:
1. Standard natural rubber latex with a high content of ammonia 0.7% by weight.
2. Natural rubber latex with a low ammonia content of 0.2% by weight in combination with zinc oxide and tetramethyl thiuram disulfide <0.035% by weight.
3. Especially high purity, double spun natural rubber latex.
Four. Natural rubber latex partly vulcanized for special applications.
For the production of adhesive masses from natural rubber, it is not necessary to perform a mastication and thus the corresponding unfolding of the natural rubber, since in the case of solvent-free aqueous adhesive masses, simply mixing the components from there is sufficient. no chewing or molecular splitting takes place by application of mechanical loads. The result of all this is a strong bond of the natural rubber / isoprene latex molecule, a high molecular weight due to lack of chewing, a wide molecular weight distribution and a low softening point Tg.
These factors determine the particularly stable balance between cohesion and adhesion of the adhesive mass resulting from the mixture of resins, and also a profile with extraordinary characteristics to enhance the performance of an adhesive tape intended for applications within a very wide range of temperatures.
The manufacture of water-based adhesive masses from natural rubber latex is a known fact. These adhesive masses, as described above, are used for making self-adhesive labels. In this case, the usual methods for the manufacture of dispersion adhesive products are followed.
Likewise, EP 0 960 923 A1 describes the production of adhesive mass systems containing natural rubber latex. Here, on the one hand, the manufacture of dispersion adhesive masses is disclosed and, on the other, the introduction of natural rubber latex into other adhesive systems from natural rubber by means of kneaders, mixers or extruders. These adhesive compositions produced in this way can be used to cover films or webs.
In this case, no improvement is described in terms of the characteristics of the packages using this type of adhesive tapes, found after a subsequent controlled crosslinking of the adhesive masses, which could be transferred to the scope of a practical production process.
For the use of variants of adhesive masses from natural rubber latex, it is not necessary to carry out a subsequent crosslinking, as already mentioned above, in order to achieve a well-studied behavior of the packaging such as that offered by the majority of the other adhesive mass systems.
By using the stabilizing resin dispersions described above as well as by using natural rubber latex, which means that the rubber does not unfold by mechanical means, there is the possibility of elaborating, transforming and coating with adhesive masses from natural rubber latex and thus the manufacture of adhesive tapes, since these adhesive masses have a very high cohesion and therefore offer optimum safety for packaging.
Not only for adhesive tapes specially designed to close boxes, but also for other adhesive tapes used in other packaging systems, such as reinforcing straps, for which a sufficient cohesion of the adhesive mass made from natural rubber is necessary. .
This positive behavior, due to the coverage of a wide range of temperatures, has been used for the adhesive tapes described in JP 56 030 481, made with an adhesive mass prepared from natural rubber latex. When using natural rubber latex, a behavior at low temperatures has been found that allows these masses to be designated as insensitive to shock.
Another point to consider is that natural rubber latex is distinguished by an extraordinarily wide field of applications, so that natural rubber latex is, on the one hand, applicable as adhesive masses for materials intended for packaging and on the other hand also suitable for applications outside of adhesive technology.
A drawback for systems that use adhesive masses made from natural rubber latex is the poor stability of the raw material of natural rubber latex with respect to mechanical loads and the effect of coagulation linked to natural rubber latex for these. adhesive masses. This sensitivity to shear conditions the limited handling capacity and field of application of natural rubber latex for the technology of adhesive masses and the adhesive tape industry. There is no known case of the manufacture of adhesive tapes in which the adhesive mass contained, made from natural rubber latex, has been applied at high speed on a sheet.
IS 2 256 286 T3
By using dispersions of stabilizing resins and / or surface-active substances, such as emulsifiers, the stability of the natural rubber latex can be considerably increased. However, with the increase in the stability of the natural rubber latex by means of superficially active substances in high concentrations, a corresponding loss of the cohesion of the adhesive mass is obtained, so that, in this case, it is necessary to find a balance between stabilization and sufficient cohesion.
The widespread use of natural rubber latex for adhesive masses as well as that of latex stabilizing resin dispersions is described in "Tackified waterborne adhesive for PSA tapes", JG De Hullu, European Adhesive & Sealants, 12 (1998), pp 11-12. By applying this type of dispersions of stabilizing resins for natural rubber latex, it will open the way to the transformation as well as the coating to the adhesive masses made from natural rubber latex. With the problem-free delivery of adhesive compositions in the form of dispersions on a polymeric support, the possibility exists of producing adhesive tapes with practicality both from the technical and economic point of view. The use of appropriate formulations for the adhesive masses, with the correct adjustment and technical use of the installations for the coating, will make the introduction of this technology possible.
The application and development of an adhesive tape, which is easily unwound and suitable for the conditions required for use in packaging, is not described in this context by JG de Hullu. The use of adhesive tapes that can be easily unwound, especially those intended for closing cardboard boxes, is of great importance in the packaging industry, in order to reduce the acoustic load of the packaging rooms and thus increase performance labor. The possibility of allowing a silent unwinding is of fundamental importance, to place the adhesive tape for packaging in a segment from medium to superior price-performance.
Adhesive packaging tapes, specifically for closing cardboard boxes, are applied in the packaging industry manually or by machine. In both cases, but especially in large packaging lines and rooms, the absence of noise, the unwinding without crackle are an additional advantage of adhesive packaging tapes in order to provide a pleasant working environment. This is an essential qualitative characteristic required in Europe for adhesive tapes intended for packaging.
For such cases for adhesive tapes that unroll silently, levels lower than 80 dB (A) measured at a distance of 25 cm have been determined, while adhesive tapes for packaging that unroll with noise and crackle, reach values clearly higher in dB (A). This has been described in "Sound level determinations, Internal Investigation Report of Beiersdorf AG"
Adhesive tapes currently on the market, provided with a stretched polypropylene backing, can be classified according to the adhesive mass, into the following types:
• Adhesive tapes with an adhesive mass made from natural rubber (a) containing solvent products.
• Adhesive tapes with styrene-isoprene-styrene hot-melt adhesive (b) • Adhesive tapes with water-based acrylate dispersions (c) (a) Adhesive tapes for packaging with a polypropylene base and an adhesive mass made from rubber natural containing solvent products, they unroll according to the mass, silently. For this it is necessary to have a flexible and soft dough. However, in most cases such types of adhesive tapes are provided with a carbamate coating containing solvent products in order to reduce the unwinding force. The back side lacquering makes the tape unroll with noise and crackle.
(b) Adhesive tapes for packaging with a polypropylene base with an adhesive mass made from a styrene-isoprene-styrene hot-melt adhesive that can only be used in combination with a suitable coating for the back side. Without the lacquering of the rear face, due to the chemical structure of the mass, the unrolling force of the adhesive tape would be so high that the support could deteriorate when unrolling, and with this, the packaging conditions would qualitatively deteriorate. considerable. The lacquering of the back face in most cases, consisting of a lacquer with carbamate containing solvents, makes the adhesive tape unwind, emitting a very high noise and crackling.
(c) Adhesive tapes for packaging on a polypropylene base with an adhesive mass made from water-based acrylates, are used in combination with a corona treatment of the back face, that is, the one away from the support face in which the adhesive mass is applied. Without the corresponding corona treatment on the back side, these adhesive tapes unroll noisily and crackly. By suitably adjusting the corona treatment to the back side you can facilitate a quiet and crepitation-free unwinding of the adhesive packaging tape.
This effect has been described in document EP 0 096 841. By means of this corona treatment of the rear face of the support face, for example after coating during the cutting process, the unwinding force of the tape
ES 2 256 286 T3 adhesive rises and thus prevents the detachment of the adhesive mass from the support. This detachment of the adhesive mass from the support, due to the unwinding process, causes a noisy and crackling behavior. By corona treatment, of the back side at a suitable intensity, the adhesive tape can be unrolled silently. For this, the unwinding force for the rear side is suitably adjusted by the corona treatment and thus the unwinding behavior is also adjusted. Up to the current level of development, all adhesive tapes are unrolled producing noise since no corona treatment has been applied to the back side.
Corona treatment for adhesive tapes brings considerable disadvantages on its part. In the first place, it is linked to an additional operational step that calls for additional machinery equipment. In the case of corona treatment, only cutting machines with a corona cutting system can be used for the cutting process. This partly requires the provision of additional machinery. Secondly, the precision of the intensity of the corona treatment is decisive, to achieve the desired effect. This entails a great insecurity of the process that forces to reinforce the quality controls.
In the event of a poor intensity of corona treatment, the desired effect that is intended for silent unwinding will only be partially achieved, since the resulting finished adhesive tapes cannot be re-operated resulting in wasted production. In case of applying an excessive intensity for the corona treatment, the force necessary for the unwinding will be raised excessively, which will cause an over-elongation of the support, the tearing of the same or a transfer of the adhesive mass will be caused during the unwinding of the Scotch tape.
Adhesive tapes for packaging with a stretched polypropylene backing and a water-based adhesive mass, which unroll silently, without applying any treatment on the side away from the backing tape, are not known and do not correspond to the level of the art. the adhesive is applied, be it for example a corona treatment.
Adhesive tapes for packaging with an adhesive mass made from natural rubber latex, can combine the advantages of a water-based adhesive mass with the disappearance of the no longer necessary corona treatment of the rear face and thus provide adhesive tapes of silent unwinding and free from crackle.
In general, the application of natural rubber latex as a component for adhesive masses is known, which, among other documents, has also been described in patents. The field of application of such adhesive masses, starting from natural rubber latex, are applications in the field of labeling and in plastering technology.
Monoaxially and biaxially stretched sheets of polypropylene are used in large quantities for adhesive tapes for packaging. Whereas, for the application of an adhesive tape for packaging, destined to the closure of cardboard boxes, biaxially stretched polypropylene sheets are preferably used. Monoaxially stretched polypropylene sheets are used in the field of reinforcing strips. They have high breaking strength and low elongation in the longitudinal direction and are very good for bundling bundles and pallet clamping. When adhesive masses are used which have insufficient cohesion or a poor anchoring of the adhesive mass on the sheet, the pallets skew due to sliding of the strips and hence the insufficient security of the pallets. Insufficient anchoring of the adhesive mass on the sheet, in the case of tapes used for closing cardboard boxes, leads to the anticipated opening of the sealed cardboard box.
Thermoplastic sheets based on polyvinyl chloride (PVC) are used for the manufacture of adhesive tapes by various manufacturers. On the other hand, it is necessary to distinguish above all the films based on PET (polyethylene terephthalate) for their very high elongation at break and a heat resistance of 130 ° C to 175 ° C as well as their good resistance against dilute acids and bases. Polyester films also have very high friction resistance and dielectric strength, but nevertheless, due to their relatively high price compared to films made from polyolefins, they have not managed to penetrate as widely in the field of adhesive tapes for packaging.
In the manufacture of adhesive tapes with adhesive masses from natural rubber, both water-based and solvent-based primers are used as adhesion agents between the adhesive mass and the backing film. These adhesive agents used partly have a crosslinking effect on the adhesive compositions applied in solution from natural rubber.
The objective of the present invention is to manufacture adhesive tapes with sheets from solvent-free stretch-oriented polyolefins, while achieving water-based adhesive masses from natural rubber latex, which offer a silent unwinding behavior, without The need to activate the opposite side of the adhesive mass of the tape by means of corona treatment.
In addition, these adhesive tapes will need to be unrolled easily. For this, the new adhesive tapes must be especially indicated as adhesive tapes for packaging of the type of the usual cardboard boxes on the market.
IS 2 256 286 T3
This objective has been solved by means of an adhesive tape such as that presented in the main claim. The subject of the sub-claims will consist of favorable developments of the object of this invention. For its part, the invention also relates to the proposed application of the adhesive tape to which it refers.
Accordingly, the invention relates to an adhesive tape with a self-adhesive finish on one side, with a sheet made from a stretched polyolefin, in which the side of the sheet away from the adhesive layer does not receive any surface treatment. .
The sheet is covered on one of its sides, with an adhesive layer that has been made as a mixture containing 65% by weight of natural rubber latex 35 to 79% by weight of an aqueous dispersion of resins from a hydrocarbon resin
According to the invention, the films used can be those made from monoaxially and biaxially drawn polyolefins, as well as films made from stretched polyethylene or drawn copolymers containing ethylene and / or polypropylene fractions.
Monoaxially stretched polypropylene is distinguished by its very high resistance to breakage and low elongation in the longitudinal direction, being used, for example, for the manufacture of strips. Especially preferred for the manufacture of adhesive tapes as referred to in the invention, for tying bales, for securing boxes and other palletized goods, are the monoaxially stretched sheets made of polypropylene.
The thickness of the monoaxially stretched sheets, made from polypropylene, are preferably of the order between 25 and 200 pm, with those from 40 to 130 pm being especially preferred.
Monoaxially stretched sheets are for the most part single-layer, although in principle monoaxially stretched multilayer sheets can also be manufactured. The best known films are those with one, two and three layers, the number of layers being a quality that is also in high demand.
Apart from this, for the manufacture of adhesive tapes according to the invention, among other applications, those which serve to secure the closure of cardboard boxes, consisting of biaxially stretched sheets made from polypropylene with a longitudinal stretch ratio, are particularly preferred. between 1: 4 and 1: 9, the preferred draw ratio being between 1: 4.8 and 1: 6, as well as with a cross-direction draw ratio between 1: 4 and 1: 9, with the draw ratio between 1: 4.8 and 1: 8.5 being preferred.
The modulus of elasticity achieved in the longitudinal direction, measured with a 10% elongation according to the ASTM D882 standard, is generally between 1000 and 4000 N / mm<sup>2</sup>, preferring the one between 1500 and 3000 N / mm<sup>2</sup>.
The thickness of the biaxially stretched sheets made from polypropylene is especially between 15 and 100 pm, with the range between 20 and 50 pm being preferred.
The biaxially stretched sheets made from polypropylene can be made by means of the extruded sheet blowing system or in the usual facilities for the manufacture of flat sheets. Biaxially stretched sheets can be made both single and multi-layer. In the case of multilayer sheets, the thicknesses and composition of the different layers can be identical, although sheets of different thickness and composition are also known.
Especially preferred for the adhesive tapes to which the invention refers are single-layer monoaxially or biaxially stretched sheets, but also multilayer biaxially or monoxially stretched polypropylene sheets, which offer a sufficiently firm bond between their layers, since peeling off layers during application would be counterproductive.
The holding power of the adhering agent on the sheet of thermoplastic material, in this case a polyolefin can be improved by flame treatment or corona treatment, since precisely the surfaces of the stretched polyolefin sheets can be manipulated by these generally known procedures, such as corona treatment or flame treatment. In any case, surface treatments using the corona system are preferable.
The article “Surface pretreatment of plastics for adhesive bonding” / A. Krüger; G. Krüger, A. Baalmann and OD Hennemann; J. Adhesion Sci. Technol., Volume 9, No. 12, pp 1611-1621 (1995), contains, for example, a summary on procedures for surface treatment.
IS 2 256 286 T3
The biaxially stretched sheets for the manufacture of the adhesive tapes to which the invention refers, on which the previous flame or corona treatment is given, on the side away from which the mass is applied and, if necessary, the eventual Adhering agent, although always, without any surface manipulation either by flame or by corona treatment on the side away from which the mass is applied.
In another preferred embodiment of the invention, between the sheet treated to the crown or to the flame and the layer of adhesive, if the case requires it, the application of an adhering agent is foreseen, to guarantee the perfect union between the adhesive mass and the foil, as well as the crosslinking of the adhesive mass.
The adhering agent optionally applicable between the adhesive mass and the carrier film serves to improve the bond between the mentioned layers.
The application of the adhesive layer is in the order of 10 to 45 g / m<sup>2</sup>. Although in one of the preferred embodiments the layering is set between 13 and 28 g / m<sup>2</sup>.
In an especially preferred variant, the adhesive compositions of the tapes to which the invention relates contain between 45 to 60% by weight of natural rubber latex. Furthermore, according to the invention, other natural rubber latexes as well as mixtures of different types of these can also be used.
Depending on the application, the following additives can be added to the adhesive masses by selecting them independently from each other:
a) 0.1 to 5% by weight of an anti-aging agent
b) 0.05 to 5% by weight of an antifoam
c) 0.05 to 4% by weight, 3% by weight especially
0.3 up to an alkoxylated alkylphenol
d) 0.05 to 20% by weight at least of a coloring pigment
Furthermore, the adhesive layer will preferably contain up to 20% by weight, at least of a resin dispersion based on hydrocarbon resins with a softening point of 20 ° C to 85 ° C.
The adhesive composition may in principle contain 0.05 to 20% by weight and preferably 2 to 15% by weight of additional resin dispersion.
As raw material for the adhesive tapes to which the invention refers, standard natural rubber latex with an ammonia content of 0.7% by weight will preferably be used, on the one hand because the mentioned natural rubber latex offers a advantage in price and on the other hand for its relatively high content of ammonia that facilitates a good stabilization of the natural rubber latex.
Natural rubber latex is especially suitable for making adhesive masses for adhesive tapes. Given their very high molecular weight, the links of the molecular chains, their low glass transition temperature and the unnecessary chewing, for the preparation of adhesive masses, natural rubber latexes offer the adhesive masses made from them, an extraordinary balance between adhesion and cohesion.
With the use of adhesive masses made from natural rubber latex, that is to say, water-based natural rubbers, it is no longer necessary any type of mechanical unfolding of the rubber. The prepared adhesive mass is distinguished by its excellent cohesion.
Its characteristics provide an extraordinarily high safety to the packaging when adhesive tapes made with these masses made from natural rubber latex are used, especially when critical types of cardboard are used and low temperatures intervene.
Likewise, the mechanical stability of natural rubber latex can be critical, in relation to mechanical shear loads.
In such cases, strong mechanical shear loads can lead to coagulation of the natural rubber latex and thus prevent its proper industrial transformation. The possibilities of stabilizing adhesive compositions made from natural rubber latex with respect to mechanical loads are, on the one hand, the addition of suitable stabilizing agent resins and, on the other, the use of emulsifiers.
The adhesive tapes to which the invention refers, preferably contain natural rubber latex at levels between 30 to 65% by weight of standard natural rubber latex, with a high ammonia content.
The solids content is preferably between 50 and 55% by weight.
IS 2 256 286 T3
Aqueous resin dispersions, that is, resin dispersions in water, are known. Its elaboration and properties are described for example in "Resin Dispersions", Anne Z. Casey in the manual of Pressure Sensitive Adhesive Technology, second edition, edited by Donatas Satas, of Nostrand Reinhold New York, pp.545- 566.
Hydrocarbon resin dispersions are also known and for example those from Hercules BV are marketed under the trade name Tacolyn.
For the adhesive tapes referred to in the invention, resin dispersions from modified hydrocarbon resins are used as main resin components. The adhesive composition contains from 35 to 70% by weight of the resin dispersion, with resin dispersions containing between 40 to 55% by weight being preferred. The solids content of the resin dispersion is between 40 and 70% by weight, with dispersions containing 45 to 60% by weight being preferred.
According to the invention, resin dispersions from mixtures of various hydrocarbon resins as well as mixtures between other resins and the hydrocarbon resins to which the invention relates also find application.
Also known are the dispersions of resins based on modified hydrocarbons, being especially interesting in this case the dispersions of C5 / C9 hydrocarbon resins, which have been modified with aromatics. In this case, the polarity of the resin dispersion and thus the adhesive composition can be adjusted by the aromatic fraction contained. Apart from the polarity of the adhesive, the hardness of the resins is also influenced. The lower the aromatics content, the lower the polarity of the modified hydrocarbon resin dispersions.
Age-inhibiting agents are known for adhesive compositions made from natural rubber. Three different types of agents for the inhibition of aging are used especially as antioxidants for adhesive compositions. Protective agents, aging inhibitors based on amines, dithiocarbamates and based on phenols, are very active, especially those indicated based on phenols due to the influence of ultraviolet radiation and sunlight.
For the adhesive tapes to which the invention relates, age-inhibiting agents based on phenols are used. According to the invention, other types of aging inhibiting agents can be used, such as, for example, protective agents, aging inhibitors based on amines and dithiocarbamates.
Organic and inorganic pigments are known for adhesive compositions made from natural rubber. For coloring adhesives made from natural rubber, titanium dioxide and titanium dioxide are used in particular in combination with other coloring pigments of different shades.
For the adhesive tapes to which the invention relates, suitable organic and / or inorganic coloring pigments are used as dispersions. The tackifying compositions preferably contain from 0.05 to 20% by weight of a well-organic inorganic coloring pigment. Furthermore, according to the invention, the use of pigments from mixtures of different organic and inorganic pigments is permitted.
The use of alkoxylated alkylphenols as plasticizers is proposed for example in the publication "Modification of Acrylic Dispersions", by Alexander Zettl in the manual of Pressure Sensitive Adhesive Technology, second edition, edited by Donatas Satas, Van Nostrand Reinhold New York, p.471. The characteristics of the alkoxylated alkylphenols are determined by the alkyl moiety and predominantly by the cleavage of the polyglycolic ether chain. In a preferred embodiment, propoxylated alkylphenol is used. These are preferably the water-soluble alkoxylated alkylphenols.
The use of polyglycol alkylphenol ether as an emulsifier for stabilizing adhesive masses in dispersion of natural rubber latex is proposed, for example others, in the publication "Compounding Natural Latex in water-based PSA's". natural latex in water-based systems of pressure sensitive adhesives), Richard C. Oldack and Robert. E. Bloss in Adhesive Age, April 1979, pp 38-43.
The characteristics and the stabilizing effect of the alkoxylated alkylphenols or, in general, of the polyethylene oxyethanolate condensates, are predominantly determined by the polyglycol ether chains. Here, moreover, there is a relationship between the chain length of the polyglycol ether and the stabilizing effect for the natural rubber latex.
The adhesive compositions to which the invention relates may contain from 0.05 to 5% by weight of alkoxylated alkylphenol, a content of from 1 to 3% by weight being given for a preferred embodiment.
When unwinding, the adhesive tape causes a noise level of less than 80 dB (A) measured at a distance of 25 cm from the center of the roll of the adhesive tape and with an unwinding speed of 45 m / min.
The manufacture of adhesive tapes according to the invention can be carried out by known processes. A summary of the usual manufacturing procedures can be found for example in the publication “Coating Equip9
ES 2 256 286 T3 ment ”(Equipment for coatings), Donatas Satas in the manual of Pressure Sensitive Adhesive Technology, second edition edited by Donatas Satas, Van Nostrand New York, pp. 708-808. Well known procedures for drying and cutting adhesive tapes will also be found in this manual.
The adhesive tapes to which the invention relates are suitable for a large number of adhesive tape applications. An important field of application is its use in the packaging sector. Adhesive tapes are especially indicated as tapes for closing cardboard boxes, adhesive tapes for packaging in general, strapping, adhesive tapes for closing plastic packaging and plastic bags. Adhesive tapes are used to secure the pallets. Other applications are bundles of loose goods and transportable items, such as tubes, wooden bars etc. The adhesive tapes referred to in the invention can be used to secure transport, say for the case of refrigerators and other electrical and electronic devices. Other applications are in the protection of labels, protection of surfaces, as it happens in the construction sector and as tear tapes for packaging. Likewise, other applications in the office sector are also possible.
Adhesive packaging tapes are made in special lengths up to 66, 100 and 1000 m. As the width of the rolls, 18, 24, 36, 48, 50 and 72 mm are generally demanded.
The most popular colors are brown, white and transparent. The prints are made on rolls of 144 or 150 mm wide, which are finally cut again to the aforementioned widths.
It should still be noted that the side opposite to the one that serves as a support for the adhesive mass of the adhesive tape must not be activated by any corona treatment. In this way, a technically expensive additional process step can be saved.
The pertinent clarifications regarding the invention will be given below with the aid of examples, without this implying in any way any limitation on the invention.
Examples
Example a
Sheet
A biaxially stretched sheet made from polypropylene from Radici is used.
Sheet thickness 28 pm
Radil T characterization
Firm / Manufacturer Radici SpA
Longitudinal elongation at break 130%
Transverse elongation at break 50%
Longitudinal modulus of elasticity 2500 N / m2m
Transverse modulus of elasticity 4000 N / m2m
The surface energy of the untreated sheet of the reference BOPP Radil T25 is less than 30 mN / m. The surface energy of the surface of the polypropylene, coated with the bonding agent, is 44 to 46 mN / m after corona treatment.
The surface energy of the raw polypropylene surface of Radil T25 sheet is less than 30 mN / m. This corresponds to the face of the sheet opposite to that of the adhesive mass.
Example b
Components (edit)
Components used:
b1 the adhesive mass b1.1 natural rubber latex supplied by Weber & Schaer, Hamburg; (solids content 60%) b1.2.1 aqueous dispersion of resins from hydrocarbon resins (from Hercules BV, Tacolyn 1070, solids content 55% by weight; softening point 70 ° C) b1.3 protective agent inhibitor of aging AD112 from Synthomer GmbH, Frankfurt
ES 2 256 286 T3 b1.4 defoamer-Foammaster 306 from Henkel, Dusseldorf b2 primers b2.1 Trapylen 6965W (generally chlorinated polypropylene dispersion from Tramaco, Hamburg, as well as Butofan LS1o3 (styrene-butadiene dispersion from BASF firm)
Example c
Formulas c1 Formula for adhesive mass
The formula is provided in percentages by weight:
Dispersion of natural rubber 52% by weight
Tacolyn 1070 47% by weight
Aging inhibiting agent 0.7% by weight
Defoamer 0.3% by weight c2 Primer formula B
The formula is provided in percentages by weight:
Trapylen 6965W 100% by weight, or
Butofan LS103 100% by weight
Example d
Manufacture of an adhesive mass and a primer
The preparation of the adhesive mass A for coating will be carried out as follows:
d1 The resin dispersion will be added to the natural rubber latex, stirring constantly with a standard mechanical stirrer at a temperature of 23 ° C. Then continue to stir more carefully for 15 min.
d2 In the mixture of step 1 (d1) the aging inhibitor agent and the antifoam will be added, stirring carefully. Then continue stirring for 15 min. The coating is then carried out.
The preparation of the primer with formula B is carried out as follows: d3 The products Trapylen 6965W and Butofan LS103 will be added and mixed without any other previous treatment. Example e
The coating
The coating of the sheets a with the primer formula B and the formulas A and B corresponding to the adhesive mass is carried out by means of a wire scraper. Here a first layer of primer is applied, it is subjected to a brief drying at 80-90 ° C and then directly, a second layer (continuous or discontinuous), of adhesive mass is applied on the primer layer.
The wire scraper and the coating speed are adjusted so that after drying of the coated film, a mass addition of approx. 18 g / m<sup>2</sup> and a primer supply of 0.6 to 0.8 g / m<sup>2</sup>. The coating was carried out in a painting facility at the Technical Institute's facilities, with a useful working width of 500 mm and a coating speed of 10 m / min. After the coating station, equipped with a dosing mechanism with a wire scraper, it was passed to a drying channel, which provided hot air (approx. At a temperature of 100 ° C). The coated sheet was made with measures of 50 mm of width by 60 m in length. The determination of the technical data related to the bonding was carried out after exposure for two days at 23 ° C and after exposure to 23 ° C for a period of one to three months.
IS 2 256 286 T3
Example f
Results
The test methods applied will be briefly specified below:
To determine the applied mass dosage, a circular sample of known surface content will be cut from the coated sheet and its weight will be determined. Next, the adhesive mass will be removed by dissolving it with gasoline and the sheet, once free of adhesive mass, will be weighed again. By the difference the quantity of mass dosed in g / m will be calculated<sup>2</sup>.
To characterize the capacity to grip the cardboard box, the adhesive tape will be applied with a manual unwinding reel of the usual ones on the market, on the cardboard box and it will be compressed with a 2 kg heavy steel roller (passing the roller twice in a row). After a waiting period of 3 min, the adhesive tape will be removed, pulling parallel to the surface of the cardboard box and at an angle of approx. 130 ° with a speed of 30 m / min. The evaluation of the gripping capacity on the cardboard box is carried out qualitatively as a function of the amount of torn paper fiber, comparing it with that of an adhesive tape for packaging, usual on the market such as tesapack 4124 from Beiersdorf, whose gripping ability is very well characterized.
To determine the safety of packaging, a standard cardboard box will be closed (cardboard shipping box; 425 mm x 325 mm x 165 mm: length x width x height: from Europakarton; made with cardboard 125 g / m double wave corrugated<sup>2</sup> with its outer layer of Kraftliner) using an automatic device for packaging of the usual ones on the market (from Knecht, model 6030 and packaging group 6230, model without braking distance) to apply the adhesive tape. The adhesive tape is applied centrally with the usual U-shaped closure, so that 60 mm of adhesive tape is applied to the front faces each. The cardboard box is completely filled with peas, before proceeding with its closure, and they are stored by laying them flat on their side faces at 40 ° C and 23 ° C. The packaging security is very well characterized, if the cardboard box is kept closed for more than 30 days. On the other hand, we proceed to characterize and describe, comparing with a reference adhesive tape (see table) the slippage of the adhesive tape on the cardboard box, as well as the general behavior of the adhesive tape in the different gluing points.
The determination of the noise produced by unwinding is carried out by unwinding the adhesive tape at a speed of 45 m / min. In this case, the unwinding noise is determined in dB (A) at a distance of 25 cm from the center of the roll of the adhesive tape with a device for measuring the volume of the sound, the usual ones on the market, in this case one of Brüel & jear (type 2226). A sound volume lower than 80 dB (A) will be considered silent.
Determination of the unwinding force. It takes place at a constant unwinding speed of (30 m / min) by measuring the turning moment and calculating the unwinding force according to known formulas in N / cm.
The result of the analysis of an adhesive tape as referred to in the invention, with unpunched sheets and with the estimation in relation to similar adhesive tapes, are listed in Table 1.
TABLE 1
Behavior of the adhesive tapes to which the invention refers
<td>Constitution / Storage Period / Temperature</td><td>Sample A</td><td>Sample B</td><td>Sample C</td><td>Sample D</td>
<td></td><td></td><td>tesa 4024 with crown on the back faces</td><td>tesa 4024 without treatment on the posterior faces</td><td>tesa 4089 with lacquered on the back faces</td>
<td>Adhesive mass</td><td>Adhesive mass A</td><td>Acrylate dispersion</td><td>Acrylate dispersion</td><td>Natural rubber compound with solvents</td>
<td>Medium</td><td>Plate a</td><td>Plate a</td><td>Plate a</td><td>Plate a</td>
<td>Primer</td><td>Formula B</td><td>Without primer</td><td>Without primer</td><td>Primer standard</td>
<td>Adhesive mass dosage [g / m<sup>2</sup>]</td><td> 18-22</td><td> 24</td><td> 24</td><td> 20</td>
IS 2 256 286 T3
TABLE 1 (continued)
<td>Constitution / Storage Period / Temperature</td><td>Sample A</td><td>Sample B</td><td>Sample C</td><td>Sample D</td>
<td>Primer coat dosage [g / m<sup>2</sup>]</td><td> 0,8</td><td></td><td></td><td> 0,6</td>
<td>Rear face surface tension</td><td>-30 mN / m</td><td>-36-38 mN / m</td><td>-30 mN / m</td><td>Carbamate lacquer</td>
<td>Anchoring the mass</td><td>Good</td><td>Good</td><td>Good</td><td>Good</td>
<td>Unwinding behavior [quiet / noisy]</td><td>silent</td><td>silent</td><td>loud</td><td>loud</td>
<td>Unwinding force at 30 m / min [N / cm]</td><td> 3,3</td><td> 4,5</td><td> 1,5</td><td> 0,7</td>
<td>Packaging safety</td><td>Very good</td><td>Good</td><td>Good</td><td>Good</td>
<td>Gripping behavior on the cardboard box</td><td>Good</td><td>Very good</td><td>Very good</td><td>Good</td>
<td colspan="5">Sample A: Sample corresponding to an adhesive tape according to the invention and without the application of corona treatment on the back side</td>
Contents10
9 members in 6 offices
Priority claims5
| Document | Office | Kind | Date |
|---|---|---|---|
| 10036705 | Germany | A | |
| 10036705 | Germany | A | |
| 20001036705 | Germany | – | |
| 1003670501962882 | – | – | – |
| DE2000136705 | – | – | – |
Members9
| Document | Office | Kind | |
|---|---|---|---|
| WO0210304A1 | World Intellectual Property Organization (WIPO) | A1 | |
| DE10036705A1 | Germany | A1 | |
| EP1311645A1 | European Patent Office (EPO) | A1 | |
| JP2004505163A | Japan | A | |
| US2004053023A1 | United States of America | A1 | |
| EP1311645B1 | European Patent Office (EPO) | B1 | |
| DE50108805D1 | Germany | D1 | |
| ES2256286T3This record | Spain | T3 | |
| US7294396B2 | United States of America | B2 |
Numbers
- Publication
- 2256286
- Publication, DOCDB
- 2256286
- Publication, EPODOC
- ES2256286T
- Application
- 1962882
- Application, DOCDB
- 01962882
- Application, EPODOC
- ES20010962882T
Titles2
- Spanish
- CINTA ADHESIVO ESPECIAL PARA EMBALJES.
- English
- SPECIAL ADHESIVE TAPE FOR PACKING.
Classification
- CPC, 11
- C09J7/243
- C09J2407/00
- Y10S428/91
- C09J7/383
- Y10T428/2848
- Y10T428/2857
- Y10T428/24959
- Y10T428/28
- Y10T428/2843
- Y10T428/26
- Y10T428/31833
- IPC, 3
- C09J7 02
- C09J107 02
- C09J201 00