Packaged viscoelastic polymer mass

Abstract

A process for producing a packaged viscoelastic polymer mass, comprising the steps of: a) providing and plasticising a viscoelastic polymer mass at elevated temperatures, wherein the polymer mass is a polymer mass based on poly(meth)acrylates having a weight-average molecular weight of 500,000 g / mol or more; b) continuously filling the plasticized viscoelastic polymer mass into a protective polymer film which has no self-adhesive properties and which was brought into a tubular shape before being filled with the viscoelastic polymer mass, to obtain a strand-like polymer composite with a diameter of 55 to 70 mm comprising a core made of the plasticized viscoelastic polymer mass and a shell made of the protective polymer film, wherein the proportion of the protective polymer film based on the total weight of protective polymer film and viscoelastic polymer mass is less than 1.0 wt.%, and wherein the plasticized viscoelastic polymer mass has a viscosity of more than 100 Pas at the time of filling into the tubular protective polymer film; c) converting the strand-shaped polymer composite into a flattened strand-shaped polymer composite whose smallest cross-section has a width to height ratio of approximately 2:1 to 7:1; d) cooling the flattened strand-shaped polymer composite to a temperature at which the polymer composite is still plastically deformable; e) and subsequently converting the flattened strand-shaped polymer composite by squeezing into an elongated polymer composite comprising a plurality of pinch points which divide the polymer composite into a plurality of first and a plurality of second regions, wherein the first regions each have a length of at least approximately 300 mm and the cross section of the first regions substantially corresponds to the cross section of the strand-shaped polymer composite, wherein the second regions are formed by the pinch points, the thickness of which results from the thickness of the protective polymer film and viscoelastic polymer mass which remains in the region of the pinch points.

Description

[0001] The present invention relates to a process for producing a packaged viscoelastic polymer mass. The present invention further relates to a packaged viscoelastic polymer mass obtainable by the process described herein, as well as to the use of the packaged viscoelastic polymer mass for further processing under the influence of heat and shear.

[0002] Viscoelastic polymer masses are well known and are frequently used in the production of adhesives. Such adhesives contain, for example, polyacrylate polymers, which are frequently produced using solution polymerization processes. If the polymerization of such base polymers takes place in a solvent, the polymer is concentrated after polymer production by removing the solvent. Subsequently, further components required to produce the adhesive are added to the polymer. Depending on the desired adhesive properties, both the properties of the base polymer and the individual components of the finished adhesive can vary considerably. To make the further processing of such polymer masses as flexible as possible and, for example, to store larger quantities of base polymer, adhesive precursors, or even the adhesive itself, the corresponding polymer masses must be packaged.

[0003] There is therefore a need to provide viscoelastic polymer masses in a storable form, which can also be made available for further processing in large-scale processes if required.

[0004] EP3004272B1 is dedicated to the provision of packaged adhesives in various forms, for example, pads, and describes packaged pressure-sensitive hotmelt adhesives comprising a pressure-sensitive hotmelt adhesive composition and a coextrusion coating consisting of pure polyethylene, pure polypropylene, or pure ethylene-vinyl acetate with a specific melt flow index. According to the prior art, the production of a self-adhesive polymer mass can be achieved by coextrusion of adhesive and protective polymer, before the encapsulated polymer is subsequently separated into portions. However, viscoelastic polymers with high molecular weights, which are suitable for the production of self-adhesive adhesives, have not yet been reliably coated with such a protective polymer.On the one hand, the processing temperatures required for this process led to the destruction of the protective polymer. On the other hand, the separation step resulted in increased internal pressure in the viscoelastic polymer, which dissipates during the subsequent storage period and leads to the opening of the protective polymer shell at these points. This results in undesirable leakage of the viscoelastic polymer.

[0005] This risk could be counteracted by using larger amounts of protective polymer. However, to minimize the impact on the properties of the viscoelastic polymers, the proportion of non-adhesive protective polymer should be as low as possible. Lower proportions of protective polymer result in the described susceptibility to external mechanical and thermal stress. It is therefore important to find a balance between the protective effect and the influence on the properties of the hot melt adhesive.

[0006] Viscoelastic polymers with high molecular weights require high processing temperatures to achieve a flowable state. High processing temperatures pose the risk of the non-adhesive protective polymer melting or becoming damaged to the point where the viscoelastic polymer escapes, making further processing impossible. Since the protective polymers are not removed during remelting but are formed into a plasticized form together with the viscoelastic polymer, protective polymers with higher softening or melting points cannot be used, as this would either result in a potentially unacceptably high processing temperature or residues of unmelted protective polymer would remain in the viscoelastic adhesive matrix. Both could have undesirable consequences for subsequent use as a self-adhesive.

[0007] However, there is still room for improvement, especially for large quantities of packaged adhesives and adhesive precursors, which are difficult to package at room temperature and exhibit high viscosities of 100 Pas or more even at elevated temperatures. In particular, there is currently a lack of suitable processes that allow the simple and efficient production of large quantities of packaged viscoelastic polymer masses. A key problem here is that the polymer masses must be heated and plasticized for packaging. Since large quantities of polymer masses store more heat than small quantities of polymer mass, a limiting factor in the large-scale production of packaged polymer masses has so far been the dissipation of the thermal energy previously incorporated into the polymer masses for improved processing. In other words, the energy used to heat the polymer masses for improved plasticization before packaging must be dissipated again.

[0008] This suggests that a compromise was necessary when packaged in large quantities of viscoelastic polymer masses. This compromise involved the significant time required to cool large quantities of polymer mass. Alternatively, many individual packages had to be produced, the contents of which could be cooled quickly. This approach is problematic, however, because, especially in the case of many small individual packages, there is a risk that the protective cover of a few packages could open, which could lead to blocking and sticking to other packages.

[0009] There is therefore still a need for efficient and rapid processes for providing large quantities of packaged viscoelastic polymer masses. In particular, there is a need for efficient and rapid processes for providing large quantities of packaged base polymers that consist essentially of poly(meth)acrylates and can be used as hotmelt pressure-sensitive adhesives. Corresponding base polymers are first produced in solvents, preferably using the free-radical polymerization process, and then freed from the solvents in a concentration process under the influence of heat and vacuum. If the base polymers produced in this way are not yet suitable as self-adhesive hotmelt pressure-sensitive adhesives, these base polymers are blended with further additives such as tackifying resins, fillers, plasticizers, crosslinkers, etc. in one or more subsequent steps.This so-called compounding of the base polymers is preferably carried out continuously in twin-screw extruders or planetary roller extruders.

[0010] A further need exists for a process that enables the processing of viscoelastic polymer masses, especially the base polymers, even in locations where there are no facilities for their polymerization or concentration. Therefore, a procedure had to be found that would allow the viscoelastic base polymers to be transported and blended into hotmelt pressure-sensitive adhesives at the intended location.

[0011] A well-known and frequently used approach for storing and transporting meltable polymers, such as hot-melt adhesives, involves filling them into smooth-walled drums. After storage and transport, the polymers are first heated using so-called drum melters to increase the flowability of the polymer mass before being fed into the further process. This form of storage is only possible under extremely complex conditions for viscoelastic base polymers with high viscosity, as the high viscosities result in only low melt flows, making the production process uneconomical.

[0012] Against this background, the present invention has for its object to provide a process for producing a packaged viscoelastic polymer mass which can be transported and stored in large quantities, wherein the process can be carried out with reduced time expenditure and sticking and blocking of individual packages is avoided.

[0013] The present invention solves this problem by a process for producing a packaged viscoelastic polymer mass, which comprises the following steps: a) providing and plasticising a viscoelastic polymer mass at elevated temperatures, wherein the polymer mass is a polymer mass based on poly(meth)acrylates having a weight-average molecular weight of 500,000 g / mol or more; b) continuously filling the plasticized viscoelastic polymer mass into a protective polymer film which has no self-adhesive properties and which was brought into a tubular shape before being filled with the viscoelastic polymer mass, to obtain a strand-like polymer composite with a diameter of 55 to 70 mm comprising a core made of the plasticized viscoelastic polymer mass and a shell made of the protective polymer film, wherein the proportion of the protective polymer film based on the total weight of protective polymer film and viscoelastic polymer mass is less than 1.0 wt.%, and wherein the plasticized viscoelastic polymer mass has a viscosity of more than 100 Pas at the time of filling into the tubular protective polymer film; c) converting the strand-shaped polymer composite into a flattened strand-shaped polymer composite whose smallest cross-section has a width to height ratio of about 2:1 to 7:1, preferably about 3:1 to 5:1; d) cooling the flattened strand-shaped polymer composite to a temperature at which the polymer composite is still plastically deformable; e) and subsequently converting the flattened strand-like polymer composite by squeezing into an elongated polymer composite comprising a plurality of pinch points which divide the polymer composite into a plurality of first and a plurality of second regions, wherein the first regions each have a length of at least approximately 300 mm and the cross section of the first regions substantially corresponds to the cross section of the strand-like polymer composite, wherein the second regions are formed by the pinch points, the thickness of which results from the thickness of the protective polymer film and viscoelastic polymer mass which remains in the region of the pinch points, wherein the second regions preferably have a length which corresponds to one to two times the maximum extension along the cross section of the first regions.

[0014] In the process according to the invention, the composite of viscoelastic polymer and protective polymer is flattened before entering the cooling bath, preferably by means of rollers, in order to achieve faster cooling of the viscoelastic polymer and thus thermal protection of the protective polymer.

[0015] Furthermore, the present invention relates to packaged viscoelastic polymer masses obtainable by the process described herein, as well as to the use and application of the packaged viscoelastic polymer mass as described herein in further processing. In a preferred embodiment of this application, the viscoelastic base polymer coated with a protective polymer is brought into a plasticized state for further processing and heated to a temperature at which the protective polymer melts and is homogeneously incorporated into the viscoelastic base polymer.

[0016] According to step a) of the process described herein, a viscoelastic polymer mass is provided and plasticized at elevated temperatures before the plasticized polymer mass is continuously filled into a protective polymer film. The viscoelastic polymer mass is a polymer mass based on poly(meth)acrylate with a weight-average molecular weight of 500,000 g / mol or more and has a viscosity of more than 100 Pas at the time of filling into the tubular protective polymer film.

[0017] "Plasticization" in the context of the present invention refers to achieving a state in which the viscoelastic polymer mass is deformable, preferably flowable. At the elevated temperatures used for plasticization, the polymer mass exhibits better deformability, i.e., increased flowability, than is the case at non-elevated temperatures. Preferably, the plasticization of the viscoelastic polymer mass is carried out at elevated temperatures in an extruder.

[0018] The viscoelastic polymer mass also has a viscosity of more than 100 Pas at the time of filling into the tubular mold. The viscosity is determined using an ARES rheometer from Rheometric Scientific Incorporation (air bearing) (Geometry Type = Parallel Plates; Diameter = 25.0 [mm]; Test Type = Rate Sweep; Temperature = 100; 120; 140; 160; 180 [°C]; Sweep Mode = Log; Initial Rate = 0.1 [1 / s]; Final Rate = 100.0 [1 / s]; Points Per Decade = 6 []).

[0019] In step b) of the process described herein, the plasticized viscoelastic polymer mass from step a) is continuously filled into a protective polymer film. The protective polymer film consists of a protective polymer that does not have self-adhesive properties. The protective polymer film is formed into a tube before filling. The tubular protective polymer film is therefore not obtained through a coextrusion process; instead, a tube shape is created from a conventional film. This is possible, for example, by starting from a web-shaped film and joining two opposite side edges of the film to form a tube. The side edges can be joined by heat and pressure.

[0020] In step b), by filling the tubular protective polymer film with the viscoelastic polymer mass, a strand-like polymer composite is obtained, comprising a core made of the plasticized viscoelastic polymer mass and a shell made of the protective polymer. According to the invention, the proportion of the protective polymer, based on the total weight of protective polymer and viscoelastic polymer mass, is less than 1.0 percent by weight. Thus, according to steps a) and b) described herein, a strand-like polymer composite is produced. This strand-like polymer composite has a diameter of approximately 55 to 70 mm, preferably 60 to 70 mm, whereby the diameter is initially circular due to the tubular shape of the protective polymer film filled in step b).

[0021] According to step c), the strand-shaped polymer composite is then converted into a flattened strand-shaped polymer composite whose smallest cross-section has a width-to-height ratio of approximately 2:1 to 7:1, preferably of approximately 3:1 to 5:1. The term smallest cross-section in this context means that the measurement is taken in a plane perpendicular to the longitudinal axis of the strand-shaped polymer composite. In other words, the cross-section is not based on the longest dimension of the polymer strand, but rather the deviation from the initially circular cross-sectional shape of the strand-shaped polymer composite from step b) is determined. The smallest cross-section and the width-to-height ratio are expressions of the extent of flattening. The flattening can be achieved by passing the strand-shaped polymer composite through a nip or rollers, for example rotating rollers.In a preferred embodiment of the present invention, flattening is carried out by means of rollers.

[0022] By converting the strand-shaped polymer composite into a correspondingly flattened strand-shaped polymer composite, the heat exchange between the strand-shaped polymer composite and the environment is greatly improved, so that step d), i.e. the cooling of the strand-shaped polymer composite (compared to a non-flattened, essentially circular cross-sectional shape), can be carried out significantly more quickly. In step d), the flattened strand-shaped polymer composite obtained in step c) is cooled to a temperature at which the polycomposite remains plastically deformable. For cooling, the strand-shaped polymer composite can, for example, be passed through a water bath used as a cooling section. At the end of step d), the core temperature of the flattened strand-shaped polymer composite is preferably less than 100 degrees Celsius, more preferably less than 90 degrees Celsius, particularly preferably less than 80 degrees Celsius.The term core temperature in the present invention refers to the temperature in the cross-sectional center of the strand-shaped polymer composite.

[0023] In step e) of the method described herein, the strand-shaped polymer composite is then converted by squeezing into an elongated polymer composite comprising a large number of pinch points which divide the polymer composite into a large number of first and a large number of second regions, wherein the first regions each have a length of at least approximately 300 mm and the cross section of the first regions substantially corresponds to the cross section of the strand-shaped polymer composite, wherein the second regions are formed by the pinch points, the thickness of which results from the thickness of the protective polymer film and viscoelastic polymer mass which remains in the region of the pinch points, wherein the second regions preferably have a length which corresponds to one to two times the maximum extension along the cross section of the first regions.

[0024] The conversion of the flattened, strand-like polymer composite by squeezing into an elongated polymer composite comprising a plurality of squeezing points ideally occurs continuously by repeatedly closing and opening a suitable tool, for example two rollers or plates, while the polymer composite is moved through the tool in its longitudinal direction. In one embodiment of the present invention, the relative movement of the polymer composite through the tool can also be interrupted in order to create the squeezing points. Ideally, the tool is designed and / or controlled such that a plurality of squeezing points can be formed one after the other, which divide the polymer composite into a plurality of first and a plurality of second regions. The first regions each have a length of at least approximately 300 mm, preferably at least approximately 500 mm, ideally more than 800 mm.The cross-section of the first regions essentially corresponds to the cross-section of the strand-like polymer composite. This means that the first regions in their middle, i.e. between two pinch points, have approximately the same cross-section and the same dimensions as the flattened strand-like polymer composite before segmentation (i.e. before conversion into the elongated polymer composite with pinch points). In the second regions of the elongated polymer composite, i.e. in the region of the pinch points, a thin film of viscoelastic polymer mass can remain. The thickness of the pinch points therefore results from the thickness of the protective polymer and the polymer mass remaining in the region of the second sections. The second regions preferably have a length, based on the longitudinal axis, i.e. parallel to the longitudinal axis, which corresponds to one to two times the maximum extent of the cross-section of the first regions.

[0025] Particularly advantageous embodiments of the process according to the invention described herein use a viscoelastic polymer mass which, when converted into the strand-like form, has a viscosity of more than 250 Pas, preferably a viscosity of more than 500 Pas.

[0026] The protective polymer film used according to the invention preferably comprises polyethylene, polypropylene, ethylene-vinyl acetate, or a mixture thereof. The proportion of the protective polymer film used in step b) based on the total weight of protective polymer and viscoelastic polymer mass is particularly preferably less than 0.8 weight percent, even more preferably less than 0.5 weight percent, based on the total weight of protective polymer and viscoelastic polymer mass. Particularly suitable proportions of the protective polymer based on the total weight of protective polymer and viscoelastic polymer mass are in the range from 0.05 to 1, preferably in the range from 0.1 to 0.8, particularly preferably in the range between 0.2 and 0.5, for example in a range from 0.25 to 0.45 weight percent.

[0027] According to a further preferred embodiment of the present invention, the viscoelastic polymer composition is an adhesive (or a precursor thereof), preferably a pressure-sensitive adhesive (or a precursor thereof). The term "precursor" in the present invention means that the viscoelastic polymer composition can be used to produce an adhesive. Most preferably, the viscoelastic polymer composition packaged by the process according to the invention is a precursor of an adhesive, ideally a base polymer. In particular, for the purposes of the present invention, a precursor of an adhesive is preferably understood to mean the precursor of a pressure-sensitive adhesive. Such a precursor can be the polymer present at the end of the polymerization of the polymers used as base polymers for the viscoelastic polymer composition.Also encompassed by the term "precursor to a pressure-sensitive adhesive" are mixtures obtained by adding various additives or components to the base polymer. The term "pressure-sensitive adhesive" as used herein is synonymous with the term "self-adhesive" or "pressure-sensitive adhesive."

[0028] For the purposes of the invention, a pressure-sensitive adhesive is understood, as is common parlance, to be a substance that is permanently tacky and adhesive, at least at room temperature. A characteristic of a pressure-sensitive adhesive is that it can be applied to a substrate by pressure and remains adhered there, whereby the pressure to be applied and the duration of this pressure are not defined in more detail. In general, however, it depends fundamentally on the exact type of pressure-sensitive adhesive and the substrate, the temperature, and the humidity, the application of short-term, minimal pressure, which does not go beyond a light touch for a brief moment, is sufficient to achieve the adhesion effect; in other cases, a longer exposure period of higher pressure may be necessary.

[0029] Viscoelastic polymer masses in the sense of the present invention are polymer masses based on poly(meth)acrylates with a weight-average molecular weight of 500,000 g / mol.

[0030] A "poly(meth)acrylate" is understood to mean a polymer obtainable by radical polymerization of acrylic and / or methacrylic monomers and, optionally, other copolymerizable monomers. In particular, a "poly(meth)acrylate" is understood to mean a polymer whose monomer base consists of at least 50 wt.% acrylic acid, methacrylic acid, acrylic esters, and / or methacrylic esters, with acrylic esters and / or methacrylic esters being present at least in a proportion, preferably at least 30 wt.%, based on the total monomer base of the polymer in question.

[0031] The viscoelastic polymer composition described herein is preferably a pressure-sensitive adhesive or a precursor thereof, wherein the pressure-sensitive adhesive preferably contains a total of 40 to 70 wt. %, more preferably a total of 45 to 60 wt. %, based in each case on the total weight of the pressure-sensitive adhesive. It may contain a (single) poly(meth)acrylate or multiple poly(meth)acrylates.

[0032] The glass transition temperature of the poly(meth)acrylate of the described pressure-sensitive adhesive is preferably <0 °C, more preferably between -20 and -50 °C. The glass transition temperature of polymers or of polymer blocks in block copolymers is determined according to the invention by means of dynamic scanning calorimetry (DSC). For this purpose, approximately 5 mg of an untreated polymer sample is weighed into an aluminum crucible (volume 25 µl) and sealed with a perforated lid. A DSC 204 F1 from Netzsch is used for the measurement. The measurement is carried out under nitrogen for inerting. The sample is first cooled to -150 °C, then heated at a heating rate of 10 K / min to +150 °C and cooled again to -150 °C. The subsequent second heating curve is again run at 10 K / min, and the change in heat capacity is recorded. Glass transitions are detected as steps in the thermogram.

[0033] The poly(meth)acrylate of the pressure-sensitive adhesive described herein preferably contains at least one partially polymerized functional monomer, particularly preferably one that is reactive with epoxy groups to form a covalent bond. The partially polymerized functional monomer, particularly preferably one that is reactive with epoxy groups to form a covalent bond, most preferably contains at least one functional group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxy groups, and amino groups; in particular, it contains at least one carboxylic acid group. Most preferably, the poly(meth)acrylate of the pressure-sensitive adhesive described herein contains partially polymerized acrylic acid and / or methacrylic acid.All of the groups mentioned exhibit reactivity with epoxy groups, which makes the poly(meth)acrylate advantageously accessible to thermal crosslinking with incorporated epoxides.

[0034] The poly(meth)acrylate of the pressure-sensitive adhesive described herein can preferably be traced back to the following monomer composition: a) at least one acrylic acid ester and / or methacrylic acid ester of the following formula (1) CH2=C(R I )(COOR II ) (1), where R I = H or CH3 and R II is an alkyl radical having 4 to 18 C atoms; b) at least one olefinically unsaturated monomer having at least one functional group selected from the group consisting of carboxylic acid groups, sulfonic acid groups, phosphonic acid groups, hydroxyl groups, acid anhydride groups, epoxy groups and amino groups; c) optionally further acrylic acid esters and / or methacrylic acid esters and / or olefinically unsaturated monomers which are copolymerizable with component (a).

[0035] It is particularly advantageous to select the monomers of component a) in a proportion of 45 to 99 wt.%, the monomers of component b) in a proportion of 1 to 15 wt.% and the monomers of component c) in a proportion of 0 to 40 wt.%, whereby the data refer to the monomer mixture for the base polymer without addition of any additives such as resins, etc.

[0036] The monomers of component a) are generally plasticizing, rather non-polar monomers. R is particularly preferred IIin the monomers a) an alkyl radical having 4 to 10 C atoms or 2-propylheptyl acrylate or 2-propylheptyl methacrylate. The monomers of formula (1) are in particular selected from the group consisting of n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentyl methacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate, n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonyl acrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, 2-propylheptyl acrylate, and 2-propylheptyl methacrylate.

[0037] The monomers of component b) are particularly preferably selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, aconitic acid, dimethylacrylic acid, β-acryloyloxypropionic acid, trichloroacrylic acid, vinylacetic acid, vinylphosphonic acid, maleic anhydride, hydroxyethyl acrylate, in particular 2-hydroxyethyl acrylate, hydroxypropyl acrylate, in particular 3-hydroxypropyl acrylate, hydroxybutyl acrylate, in particular 4-hydroxybutyl acrylate, hydroxyhexyl acrylate, in particular 6-hydroxyhexyl acrylate, hydroxyethyl methacrylate, in particular 2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, in particular 3-hydroxypropyl methacrylate, hydroxybutyl methacrylate, in particular 4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, in particular 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidyl methacrylate.

[0038] Examples of monomers of component c) are: Methylacrylat, Ethylacrylat, Propylacrylat, Methylmethacrylat, Ethylmethacrylat, Benzylacrylat, Benzylmethacrylat, sec-Butylacrylat, tert-Butylacrylat, Phenylacrylat, Phenylmethacrylat, Isobornylacrylat, Isobornylmethacrylat, tert-Butylphenylacrylat, tert-Butylaphenylmethacrylat, Dodecylmethacrylat, Isodecylacrylat, Laurylacrylat, n-Undecylacrylat, Stearylacrylat, Tridecylacrylat, Behenylacrylat, Cyclohexylmethacrylat, Cyclopentylmethacrylat, Phenoxyethylacrlylat, Phenoxyethylmethacrylat, 2-Butoxyethyl-methacrylat, 2-Butoxyethylacrylat, 3,3,5-Trimethylcyclohexylacrylat, 3,5-Dimethyl-adamantylacrylat, 4-Cumylphenylmethacrylat, Cyanoethylacrylat, Cyanoethylmethacrylat, 4-Biphenylacrylat, 4-Biphenylmethacrylat, 2-Naphthylacrylat, 2-Naphthylmethacrylat, Tetrahydrofufurylacrylat, Diethylaminoethylacrylat, Diethylaminoethylmethacrylat, Dimethylaminoethylacrylat, Dimethylaminoethylmethacrylat, 3-Methoxyacrylsäuremethylester, 3-Methoxybutylacrylat, 2-Phenoxyethylmethacrylat,Butyldiglykolmethacrylat, Ethylenglycolacrylat, Ethylenglycolmonomethylacrylat, Methoxypolyethylenglykolmethacrylat 350, Methoxypolyethylenglykolmethacrylat 500, Propylenglycolmonomethacrylat, Butoxydiethylenglykolmethacrylat, Ethoxytriethylen-glykolmethacrylat, Octafluoropentylacrylat, Octafluoropentylmethacrylat, 2,2,2-Trifluor-ethylmethacrylat, 1,1,1,3,3,3-Hexafluoroisopropylacrylat, 1,1,1,3,3,3-Hexafluoro-isopropylmethacrylat, 2,2,3,3,3-Pentafluoropropylmethacrylat, 2,2,3,4,4,4-Hexafluoro-butylmethacrylat, 2,2,3,3,4,4,4-Heptafluorobutylacrylat, 2,2,3,3,4,4,4-Heptafluoro-butylmethacrylat, 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-Pentadecafluorooctylmethacrylat, Dimethyl-aminopropylacrylamid, Dimethylaminopropylmethacrylamid, N-(1-Methylundecyl)acrylamid, N-(n-Butoxymethyl)acrylamid, N-(Butoxymethyl)methacrylamid, N-(Ethoxymethyl)acrylamid, N-(n-Octadecyl)acrylamid; N,N-Dialkyl-substituierte Amide wie beispielsweise N,N-Dimethylacrylamid und N,N-Dimethylmethacrylamid; N-Benzyl-acrylamid, N-Isopropylacrylamid, N-tert-Butylacrylamid, N-tert-Octylacrylamid, N-Methylolacrylamid, N-Methylolmethacrylamid, Acrylnitril, Methacrylnitril; Vinylether wie Vinylmethylether, Ethylvinylether, Vinylisobutylether; Vinylester wie Vinylacetat; Vinyl halides, vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide, N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene, α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3,4-dimethoxystyrene; macromonomers such as 2-polystyreneethyl methacrylate (weight-average molecular weight Mw, determined by GPC, from 4000 to 13000 g / mol), poly(methyl methacrylate)ethyl methacrylate (Mw from 2000 to 8000 g / mol).

[0039] Monomers of component c) can also advantageously be selected to contain functional groups that support subsequent radiation-chemical crosslinking (e.g., by electron beams, UV). Suitable copolymerizable photoinitiators include benzoin acrylate and acrylate-functionalized benzophenone derivatives. Monomers that support crosslinking by electron irradiation include tetrahydrofurfuryl acrylate, N-tert-butylacrylamide, and allyl acrylate.

[0040] The poly(meth)acrylates are preferably produced by conventional radical polymerizations or controlled radical polymerizations. The poly(meth)acrylates can be produced by copolymerization of the monomers using conventional polymerization initiators and, if appropriate, regulators. Polymerization takes place at conventional temperatures in bulk, in emulsion, for example, in water or liquid hydrocarbons, or in solution.

[0041] The poly(meth)acrylates are preferably prepared by copolymerizing the monomers in solvents, particularly preferably in solvents having a boiling range of 50 to 150 °C, in particular of 60 to 120 °C, using 0.01 to 5 wt.% of polymerization initiators, in particular 0.1 to 2 wt.% of polymerization initiators, in each case based on the total weight of the monomers.

[0042] In principle, all conventional initiators are suitable. Examples of radical sources are peroxides, hydroperoxides, and azo compounds, for example, dibenzoyl peroxide, cumene hydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide, cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butyl peroctoate, and benzpinacol. Preferred radical initiators are 2,2'-azobis(2-methylbutyronitrile) (vazo ® 67™ from DuPont) or 2,2'-azobis(2-methylpropionitrile) (2,2'-azobisisobutyronitrile; AIBN; Vazo ® 64™ from DuPont).

[0043] Preferred solvents for the preparation of the poly(meth)acrylates are alcohols such as methanol, ethanol, n- and isopropanol, n- and isobutanol, especially isopropanol and / or isobutanol; hydrocarbons such as toluene and especially gasolines with a boiling range of 60 to 120 °C; ketones, especially acetone, methyl ethyl ketone, and methyl isobutyl ketone; esters such as ethyl acetate, and mixtures of the aforementioned solvents. Particularly preferred solvents are mixtures containing isopropanol in amounts of 2 to 15 wt. %, especially 3 to 10 wt. %, based in each case on the solvent mixture used.

[0044] After the production of the poly(meth)acrylates (i.e. at the end of the polymerization), if a solvent is used, a concentration is carried out, and the polymer thus produced is used essentially solvent-free as a viscoelastic polymer mass in the process according to the invention.

[0045] The polymer can be concentrated in the absence of other additives such as crosslinkers and accelerators. However, it is also possible to add one of these compound classes to the polymer prior to concentration, so that the concentration then takes place in the presence of this substance(s). However, this only makes sense if the presence of the selected additives does not conflict with the process of the present invention, since according to the invention, a viscoelastic polymer mass is first prepared and plasticized at elevated temperatures (step a)) before the plasticized viscoelastic polymer mass based on the poly(meth)acrylate is filled into a protective polymer film (step b)). According to the invention, the addition of additives to the respective process steps is therefore dispensed with if the additives are incompatible with the temperatures of the individual process steps.

[0046] According to the invention, the weight-average molecular weights Mw of the poly(meth)acrylates are 500,000 g / mol and more, preferably 750,000 g / mol and more, particularly preferably 1,000,000 g / mol and more. For this purpose, it may be advantageous to carry out the polymerization in the presence of suitable polymerization regulators such as thiols, halogen compounds, and / or alcohols in order to adjust the desired average molecular weight.

[0047] The data on the weight-average molecular weights, Mw (and also on the number-average molecular weight, Mn) in this document refer to the conventional determination by gel permeation chromatography (GPC). The determination is carried out on 100 µl of a clear-filtered sample (sample concentration 4 g / l). Tetrahydrofuran with 0.1 vol.% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C.

[0048] The guard column is a column type PSS-SDV, 5 µm, 10 3Å, 8.0 mm * 50 mm (information here and below in the order: type, particle size, porosity, inner diameter * length; 1 Å = 10 -10 m) is used. For separation, a combination of columns of type PSS-SDV, 5 µm, 10 3 Å and 10 5 Å and 10 6 Å columns with a diameter of 8.0 mm x 300 mm each were used (columns from Polymer Standards Service; detection using a Shodex RI71 differential refractometer). The flow rate was 1.0 ml per minute. Calibration was performed against PMMA standards (polymethyl methacrylate calibration) for poly(meth)acrylates and against PS standards (polystyrene calibration) for other materials (resins, elastomers).

[0049] According to the invention, the viscoelastic polymer composition based on poly(meth)acrylates is a polymer composition that contains one or more poly(meth)acrylates or consists of one or more poly(meth)acrylates. Particularly preferred embodiments of the invention relate to processes in which the viscoelastic polymer composition is a self-adhesive composition or can be converted into a self-adhesive composition.

[0050] The term "convertible" in the present invention refers, for example, to situations in which the viscoelastic polymer mass can be converted into the actual pressure-sensitive adhesive by modification, e.g., by crosslinking, and / or by adding additives. Depending on the degree of crosslinking required, the viscoelastic polymer mass can be provided in the form of a crosslinked poly(meth)acrylate, or the final crosslinking to achieve the desired degree of crosslinking is only carried out when the packaged viscoelastic polymer mass is used in the application described herein for further processing under the influence of heat and shear.

[0051] If pressure-sensitive adhesives with a relatively low molecular weight and good shear strength after the crosslinking step are required, the poly(meth)acrylate of the polymer compositions described herein can have a polydispersity of, for example, PD < 4 and thus a relatively narrow molecular weight distribution. Furthermore, the lower polydispersity enables easier processing from the melt, since the flow viscosity is lower than that of a more broadly distributed poly(meth)acrylate while maintaining largely the same application properties. Narrowly distributed poly(meth)acrylates can advantageously be produced by anionic polymerization or by controlled radical polymerization methods, the latter being particularly suitable. Corresponding poly(meth)acrylates can also be produced via N-oxyls.Furthermore, atom transfer radical polymerization (ATRP) can be advantageously used for the synthesis of narrowly distributed poly(meth)acrylates, with monofunctional or difunctional secondary or tertiary halides preferably being used as initiators and Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Ag, or Au complexes being used for the abstraction of the halides. RAFT polymerization is also suitable.

[0052] The poly(meth)acrylates of the pressure-sensitive adhesive described herein are preferably crosslinked by linking reactions—in particular in the sense of addition or substitution reactions—of the functional groups contained therein with thermal crosslinkers. All thermal crosslinkers can be used which - ensure a sufficiently long processing time so that gelling does not occur during the processing process, especially the extrusion process, - as well as rapid post-crosslinking of the polymer to the desired degree of crosslinking at temperatures lower than the processing temperature, especially at room temperature.

[0053] For example, a combination of polymers containing carboxy, amino, and / or hydroxyl groups and isocyanates, especially aliphatic or blocked isocyanates, for example trimerized isocyanates deactivated with amines, as crosslinkers is possible. Suitable isocyanates are, in particular, trimerized derivatives of MDI [4,4-methylenedi(phenyl isocyanate)], HDI [hexamethylene diisocyanate, 1,6-hexylene diisocyanate], and IPDI [isophorone diisocyanate, 5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane], for example the Desmodur types. ® N3600 and XP2410 (each from Bayer AG: aliphatic polyisocyanates, low-viscosity HDI trimers). Also suitable is the surface-deactivated dispersion of micronized, trimerized IPDI BUEJ 339.® , now HF9 ® (BAYER AG).

[0054] Thermal crosslinkers are preferably used at 0.1 to 5 wt.%, in particular at 0.2 to 1 wt.%, based on the total amount of the polymer to be crosslinked.

[0055] Crosslinking via complexing agents, also known as chelates, is also possible. A preferred complexing agent, for example, is aluminum acetylacetonate.

[0056] The pressure-sensitive adhesive described herein preferably contains at least one tackifier compatible with the poly(meth)acrylate, which can also be referred to as an adhesion promoter or adhesive resin. According to the general understanding of those skilled in the art, a "tackifier" is understood to be an oligomeric or polymeric resin that increases the autohesion (tack, inherent adhesiveness) of the pressure-sensitive adhesive compared to an otherwise identical pressure-sensitive adhesive that does not contain a tackifier. A "tackifier compatible with the poly(meth)acrylate" is understood to be a tackifier that changes the glass transition temperature of the system obtained after thorough mixing of poly(meth)acrylate and tackifier compared to the pure poly(meth)acrylate, whereby the mixture of poly(meth)acrylate and tackifier can also only be assigned one Tg.A tackifier incompatible with the poly(meth)acrylate would result in two Tg values ​​in the system obtained after thorough mixing of poly(meth)acrylate and tackifier, one of which would be attributed to the poly(meth)acrylate and the other to the resin domains. In this context, the Tg is determined calorimetrically using DSC (differential scanning calorimetry).

[0057] The tackifier compatible with the poly(meth)acrylate preferably has a DACP value of less than 0 °C, very preferably of at most -20 °C, and / or preferably an MMAP value of less than 40 °C, very preferably of at most 20 °C. For the determination of DACP and MMAP values, see C. Donker, PSTC Annual Technical Seminar, Proceedings, pp. 149-164, May 2001.

[0058] The tackifier compatible with the poly(meth)acrylate is particularly preferably a terpene-phenolic resin or a rosin derivative, especially a terpene-phenolic resin. The pressure-sensitive adhesive described herein may also contain mixtures of several tackifiers. Among the rosin derivatives, rosin esters are preferred.

[0059] A pressure-sensitive adhesive as described herein preferably contains tackifiers compatible with the poly(meth)acrylate in a total amount of 7 to 25 wt. %, particularly preferably in a total amount of 12 to 20 wt. %, based in each case on the total weight of the pressure-sensitive adhesive.

[0060] Depending on the application area and the desired properties of the described pressure-sensitive adhesive, it may contain further components and / or additives, either alone or in combination with one or more other additives or components.

[0061] For example, the pressure-sensitive adhesive described herein may contain powder and granular fillers, especially abrasive and reinforcing fillers, dyes, and pigments such as titanium dioxide, zinc oxide, and / or carbon black. Various organic fillers may also be present.

[0062] The density of the viscoelastic polymer mass is preferably 1.05 to 1.3 g / cm 3 , particularly preferably 1.10 to 1.25 g / cm 3 , measured at 25 degrees Celsius.

[0063] As previously described, according to the invention, a viscoelastic polymer mass is first provided (step a)) and continuously filled into a tubular protective polymer film (step b)) before the strand-like polymer composite thus obtained is flattened (step c)), subsequently cooled (step d)) and converted into an elongated polymer composite with a plurality of pinch points. In a preferred embodiment of the invention, the elongated polymer composite is then placed in a container, preferably a box or crate. In a particularly preferred embodiment of the invention, the elongated polymer composite is placed in a container in such a way that the deposition direction of the polymer composite changes at each of the pinch points. The size of the preferably rectangular container is dimensioned such that the container has a length that approximately corresponds to the length of the first regions of the elongated polymer composite.

[0064] By segmenting the strand-like polymer composite and subsequently placing the elongated polymer composite in a container, it is ensured that sufficiently large quantities of viscoelastic polymer mass can be kept ready for transport and storage.

[0065] In a preferred embodiment of the present invention, the process described herein is carried out continuously. This means that the steps a) to e) are carried out in such a way that the polymer composite is segmented directly after step d), i.e., after cooling, and then placed in a container. For this purpose, the open ends of the polymer composite are sealed. To seal the polymer composite, the protective polymer can be glued or welded at its end, for example, by heating the protective polymer in sections and then pressing them together, as is known in a heat-sealing process.

[0066] The viscoelastic polymer mass thus produced is the subject of the present invention and is suitable for use and further processing under the influence of heat and shear.

[0067] The present invention therefore provides a method by which large quantities of finished polymer mass can be stored, transported, and further processed regardless of location. For this purpose, the packaged viscoelastic polymer mass can be removed, for example, from the container used at one end and continuously fed into an extruder. In this extruder, the packaged viscoelastic polymer mass is then plasticized and preferably melted under the influence of heat and shear, so that the protective polymer is ideally homogeneously distributed throughout the viscoelastic polymer mass. The resulting mixture of viscoelastic polymer mass and protective polymer can then be portioned and / or shaped, or the mixture of viscoelastic polymer mass and protective polymer can be admixed with further additives.

[0068] The quantities, sizes, and other measurements described herein, such as the amount of protective polymer and the dimensions of the flattened strand-like polymer composite, allow for the easy provision of large quantities of packaged viscoelastic polymer mass for transport and storage. The process can be completed in a shorter time and avoids the sticking and blocking of individual packages. At the same time, further processing of the packaged viscoelastic polymer mass into an intermediate or final product under the influence of heat and shear is ensured. For further processing, the viscoelastic polymer mass is advantageously treated together with the protective polymer in an extruder under the influence of heat and shear.

[0069] It has been shown that the continuous filling of the viscoelastic polymer mass into a protective polymer film as described herein produces a stable strand-like polymer composite that can be stored over temperature ranges from -30°C to +60°C without any leakage of the viscoelastic polymer mass. This distinguishes the packaged viscoelastic polymer mass according to the invention from pillow-shaped packaged goods, in which the individual packages repeatedly open unintentionally. Furthermore, the use of the protective polymer in the amounts described herein ensures that the protective polymer melts during further processing under the influence of heat and shear and can be distributed homogeneously throughout the viscoelastic polymer mass.

Claims

[1] Method for producing a packaged viscoelastic polymer mass, comprising the steps: a) Providing and plasticizing a viscoelastic polymer mass at elevated temperatures, wherein the polymer mass is a polymer mass based on poly(meth)acrylates with a weight-average molecular weight of 500,000 g / mol or more; b) Continuous filling of the plasticized viscoelastic polymer mass into a protective polymer film which has no self-adhesive properties and which was formed into a tube shape before filling with the viscoelastic polymer mass, obtaining a strand-like polymer composite with a diameter of 55 to 70 mm comprising a core of the plasticized viscoelastic polymer mass and a shell of the protective polymer film, wherein the proportion of the protective polymer film is less than 1.0 wt.% in relation to the total weight of the protective polymer film and the viscoelastic polymer mass, and wherein the plasticized viscoelastic polymer mass has a viscosity of more than 100 Pa at the time of filling into the tube-shaped protective polymer film; c) Converting the strand-shaped polymer composite into a flattened strand-shaped polymer composite whose smallest cross-section has a width-to-height ratio of approximately 2:1 to 7:1; d) Cooling the flattened strand-shaped polymer composite to a temperature at which the polymer composite remains plastically deformable; e) and subsequent conversion of the flattened strand-like polymer composite into an elongated polymer composite by squeezing, comprising a plurality of squeezing points which divide the polymer composite into a plurality of first and a plurality of second regions, wherein the first regions each have a length of at least about 300 mm and the cross-section of the first regions substantially corresponds to the cross-section of the strand-like polymer composite, wherein the second regions are formed by the squeezing points, the thickness of which results from the thickness of the protective polymer film and viscoelastic polymer mass which remains in the region of the squeezing points. [2] Method according to claim 1, wherein the transfer of the strand-shaped polymer composite into the flattened strand-shaped polymer composite according to step c) is carried out by means of rollers. [3] Method according to one of the preceding claims, wherein the cooling in step d) is carried out to a core temperature of less than 100 °C. [4] Method according to one of the preceding claims, wherein the strand-shaped polymer composite is deposited in a container after step e), wherein the depositing direction of the elongated polymer composite changes at crush points. [5] Method according to any of the preceding claims, wherein step d) is carried out in a water bath. [6] Method according to any of the preceding claims, wherein the plasticizing in step a) is carried out in an extruder. [7] Method according to one of the preceding claims, wherein the plasticized viscoelastic polymer mass has a viscosity of more than 250 Pas at the time of filling into the tubular protective polymer film. [8] Method according to one of the preceding claims, wherein in step b) the proportion of the protective polymer film is less than 0.5 wt.% in relation to the total weight of the protective polymer film and the viscoelastic polymer mass. [9] Method according to any of the preceding claims, wherein the protective polymer film consists of polyethylene, polypropylene, ethylene vinyl acetate or a mixture thereof. [10] Method according to any of the preceding claims, wherein the viscoelastic polymer mass is a self-adhesive mass or can be converted into a self-adhesive mass. [11] Method according to any of the preceding claims, wherein the viscoelastic polymer mass has a density of 1.05 to 1.3 g / cm³ at 25 °C 3 exhibits. [12] Packaged viscoelastic polymer mass obtainable according to a method of claims 1 to 11. [13] Use of a packaged viscoelastic polymer mass according to claim 12 in a process in which the packaged viscoelastic polymer mass is plasticized for further processing under the influence of heat and shear. [14] Use according to claim 13, wherein the protective polymer film is also plasticized during the treatment of the packaged viscoelastic polymer mass with heat and shear for further processing. [15] Use according to one of claims 13 or 14, wherein the treatment with heat and shear is carried out in an extruder.