JP2015218318A - Method for producing a syntactic foam-type polymer composition, preferably a pressure-sensitive adhesive composition, apparatus for carrying out the method, extrudate, and self-adhesive tape - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of a syntactic foam type polymer composition and a pressure-sensitive adhesive composition.SOLUTION: The method satisfies the following a) to d): a) expandable microspheres are introduced into a matrix material to be mixed; b) the expandable microspheres expand; c) the temperature distribution in a mixer 1 is nonuniform in the plane perpendicular to the transportation direction; and d) a first surface 3 as the boundary of a mixing space 2 of the mixer 1 is kept at a sufficiently high temperature in the plane perpendicular to the transportation direction of the mixer 1, such that a microsphere-containing polymer composition reaches a temperature (T) sufficient for starting and continuing the expansion as long as the polymer composition comes in contact with the surface 3, while, in the same plane perpendicular to the transportation direction of the mixer 1, a second surface 4 as the boundary of the mixing space 2 of the mixer 1 is kept at a sufficiently low temperature, such that the microsphere-containing polymer composition does not reach a temperature (T) sufficient for starting and continuing the expansion as long as the polymer composition comes in contact with the surface 4.

Description

The present invention is a method for producing a syntactic foam type polymer composition, preferably a pressure sensitive adhesive composition, comprising:
a) at least a majority of the closed-cell voids are obtained by introducing expandable microspheres into the matrix material and subsequent mixing;
b) Expansion of the expandable microspheres is performed after they are introduced into the matrix material,
c) A method is described in which the temperature distribution in the mixer (1) is non-uniform in a plane perpendicular to the transport direction of the mixer (1).

  The present invention further describes two devices for carrying out the above method, an extrudate produced by the above method, and a self-adhesive tape.

  The term “syntactic” means that at least the foam voids are completely surrounded by the matrix material and thus independent from the periphery.

  Self-adhesive compositions foamed by expandable microspheres are known. Compared to open cell foamed self-adhesive compositions, they have better sealing against dust and liquids due to their closed cells. Compared to non-foamed self-adhesive compositions, they better match the irregularities of the substrate to be bonded together. Compared to self-adhesive compositions foamed by hollow glass spheres, they are more deformable, better equalize the difference in thermal expansion between the various materials bonded by adhesion when the temperature fluctuates and vibration Dampens vibrations and blocks vibrations better.

  The thickness of the microsphere shell and the thermoplastic polymer that makes it affect the mechanical properties of the foam to the same extent as the unexpanded diameter of the microspheres and the type of blowing agent present inside them. These parameters also affect the microsphere expansion onset temperature, expansion rate, maximum expansion capacity and robustness.

  Many types of expandable microspheres are commercially available, and it is preferred to use a non-expanded type for the purposes of the present invention. This is because they have a greater expansion capacity than the expanded type. There are many types of non-expanded microspheres available from various manufacturers, and their diameters (6-9 μm for the smallest type of Expandel, ie 461DU20, and the largest type of Expandel) In the case 28-38 μm, ie 920-, 930- and 951DU120) and the temperatures required to initiate their expansion (75-220 ° C.) are essentially different. An example of a commercially available microsphere is Akzo Nobel's Expandel® DU standard (DU = dried and not expanded).

  The term “uniform” (= “uniform”) is used in the present invention to refer to a specific mass of test sample taken from the product (the length of the edge is naturally greater than the diameter of the largest expandable microsphere therein). It must be substantially large (ie, at least about 30 times the size), but is used to mean that the product is virtually unrelated to where the test sample was taken. This term therefore does not mean, for example, that all expanded microspheres must have the same size. They cannot have the same size, because their precursor, unexpanded microspheres are produced in a random process and hence individual microspheres with respect to both their diameter and wall thickness This is because there is a certain amount of variation every time.

  The production of expandable microspheres is described in principle in US Pat. No. 3,615,972 by Dow (Patent Document 1).

  German Patent No. 2105877C (Patent Document 2) describes a self-adhesive tape having a support coated with a self-adhesive composition containing microbubbles (also referred to as “pressure-sensitive adhesive”) on at least one surface. It is disclosed. This adhesive layer contains a nucleating agent and the small bubbles of the adhesive layer are closed and distributed “uniformly” in the adhesive layer.

  U.S. Pat. Nos. 6,103,152 (Patent Document 4) and 6,797,371 (Patent Document 5) corresponding to European Patent No. 11082809B1 (Patent Document 3) include a polymer foam formed of expandable microspheres. Is taught. In the invalidation lawsuit for the European patent against the German patent, the patent owner indicated that the expression “starting foaming before leaving the mold”, which means that the mold at the end of the second extruder is clearly in context, Alleged that it was actually intended to mean the beginning of foaming. The German Federal Court granted this in its July 17, 2012 decision “Polymer Foam” (accession number: XZR117 / 11, paragraph 31, final sentence).

  EP 0 257 984 A1 (Patent Document 6) describes a self-adhesive tape having a foamed adhesive layer comprising microspheres on at least one surface. According to its third page, lines 38-41, the microspheres are mixed in the adhesive composition in an unexpanded state and expand by subsequent heating, or preferably expand first. And then mixed into the adhesive composition.

  Further, German Patent No. 3537433A1 (Patent Document 7), International Publication No. 95 / 31225A1 Pamphlet (Patent Document 8), International Publication No. 95 / 32851A1 Pamphlet (Patent Document 9), European Patent Application Publication No. 0693097A1 There are documents of (Patent Document 10), pamphlet of International Publication No. 98 / 18878A1 (Patent Document 11) and German Patent Application Publication No. 19730854A1 (Patent Document 12), but the relevance is small.

  German Offenlegungsschrift 10 2008004388 A1 teaches a method for producing a non-foamed self-adhesive composition using natural rubber as the base polymer. In these contexts, Examples 5 and 6 on pages 23 and 24 teach, among other things, a production method using a planetary gear extruder. In this patent document, when the “heating zone” is shown to be the two radially outermost hollow gears of a two-module planetary gear extruder, the temperature of the hollow gear is 50 ° C. in both modules. While maintaining the sun gear (= center spindle) at only 10 ° C. has been proposed.

US Pat. No. 3,615,972 German Patent No. 2105877C EP 1102809B1 specification US Pat. No. 6,103,152 US Pat. No. 6,797,371 European Patent Application No. 0257984A1 German Patent Application Publication No. 3537433A1 International Publication No. 95 / 31225A1 Pamphlet International Publication No. 95 / 32851A1 Pamphlet European Patent Application No. 0693097A1 International Publication No. 98 / 18878A1 Pamphlet German Patent Application Publication No. 19730854A1 German Patent Application Publication No. 102008004388A1

Magazine Polymer, 1967, No. 8, page 381, ff.

  Compared to at least the products known so far (of which the one produced as described in EP 1102809B1 appears to be the closest) It is an object of the present invention to maintain the homogeneity of the mixture of microspheres and matrix mixture in a way that exposes the matrix polymer to thermal and mechanical stresses. The required mixing process should not increase the proportion of broken microspheres, and should preferably further reduce it. The crest-valley height of the foamed extrudate should preferably be reduced.

Surprisingly, the inventor found that by pursuing a phenomenon that initially seemed to be a measurement error, the uniform distribution of the microspheres when the temperature distribution in the mixer is vertically non-uniform in the transport direction of the machine. Has been found to be particularly well and efficiently achieved. In particular, according to the present invention,
d) The first surface (3) which becomes the boundary of the mixing space (2) of the mixer (1) is in contact with the first boundary surface (3) by the polymer composition containing the microspheres. As long as it should be kept at a sufficiently high temperature in a plane perpendicular to the transport direction of the mixer (1) so as to reach a temperature (T _E ) sufficient to start and continue its expansion,
e) On the other hand, in the same plane perpendicular to the transport direction of the mixer (1), the second surface (4) serving as the boundary of the mixing space (2) of the mixer (1) contains microspheres. As long as the polymer composition is in contact with this second boundary surface (4), it is kept at a sufficiently low temperature so that it does not reach a temperature (T _e ) sufficient to initiate and continue its expansion.

In a single screw extruder as a mixer, according to the present invention, it is recommended that a temperature difference be provided between the screw and the cylindrical portion. If acrylates and / or methacrylates are used as the base polymer of the matrix, optionally with a tack-enhancing resin, the temperature difference is
I: It is recommended that the screw be at least 50 ° C., particularly preferably 65 ° C. to 90 ° C., lower than the cylindrical part.

However, polyethylene and / or polypropylene and / or polyethylene-vinyl acetate and / or polypropylene-vinyl acetate and / or copolymers of some or all of these monomers are optionally used as the base polymer of the matrix, optionally together with the tackifier resin. When used, the temperature difference is reversed,
II: It is recommended that the screw is hotter than the cylindrical part, but the preferred absolute value of the temperature difference remains the same, ie at least 50 ° C., particularly preferably 65 ° C. to 90 ° C.

In a twin screw extruder as a mixer, there are various possibilities for the arrangement of the desired non-uniform temperature region in a plane perpendicular to the transport direction, ie only a distinction between high and low temperatures:
III: One screw is cold, the other is hot, the cylinder is cold,
IV: One screw is cold, the other is hot, the cylinder is hot,
V: Both screws are cold, the cylinder is hot,
VI: Both screws are hot and the cylinder is cold.

  For the purposes of the present invention, “hot” means the element temperature that heats the composition containing expandable microspheres in contact with this element sufficient for its expansion to occur, while “cold” means Means the element temperature that keeps the composition containing expandable microspheres in contact with the element at a temperature that is too low for the expansion to occur.

  The possibility V is preferred when acrylates and / or methacrylates are used as the matrix base polymer, optionally together with a tack-increasing resin. Again, the preferred absolute value of the temperature difference is at least 50 ° C., particularly preferably in the range from 65 ° C. to 90 ° C.

  On the other hand, polyethylene and / or polypropylene and / or polyethylene-vinyl acetate and / or polypropylene-vinyl acetate and / or a copolymer of some or all of their monomers are optionally combined with a tackifying resin as the base polymer of the matrix. When used, possibility VI is preferred. Again, the preferred absolute value of the temperature difference is at least 50 ° C., particularly preferably in the range from 65 ° C. to 90 ° C.

  By selecting the combination of elements in this way, both clogging in the screw or spindle bearing and blockage in the supply shaft are avoided.

In a preferred planetary gear extruder for industrial practice of the invention, it is primarily compact in structure, nevertheless has a large surface area available for temperature control, and has a particularly wide desired temperature non-uniformity. Can be set with good reproducibility in the range, and secondly, the annular structure of this type of device avoids clogging in the bearing due to different thermal expansions despite the non-uniform distribution There are many different forms of temperature differences that can occur. The structure of the planetary gear extruder is particularly simple when effective temperature control of the planetary gear ("temperature control" is used generically for "heating" and "cooling" for the purposes of this US patent application) is not required. Stay in the right things. A great many possible forms can disappear, but the following two are maintained.
VII: low temperature sun gear and high temperature hollow gear, or VIII: high temperature sun gear and low temperature hollow gear.

  When acrylates and / or methacrylates are used as the base polymer of the matrix, optionally together with a tackifying resin, the possibility in the case of a single screw extruder I and the possibility in the case of a twin screw extruder V In a similar manner, possibility VII is preferred in the case of a planetary gear extruder. In this case too, the preferred absolute value of the temperature difference is at least 50 ° C., particularly preferably in the range from 65 ° C. to 90 ° C.

  Furthermore, polyethylene and / or polypropylene and / or polyethylene-vinyl acetate and / or polypropylene-vinyl acetate and / or a copolymer of some or all of their monomers are optionally used as a base polymer for the matrix, optionally together with a tackifying resin. When used, possibility VIII is preferred in the case of a planetary gear extruder in a manner similar to possibility II in the case of a single screw extruder and possibility VI in the case of a twin screw extruder. Again, the preferred absolute value of the temperature difference is at least 50 ° C., particularly preferably in the range from 65 ° C. to 90 ° C.

  The inventor has found that possibility VII allows substantial expansion of the microspheres even during mixing in a planetary gear extruder. Such premature expansion is due to the fact that microspheres are only about 0.02 μm in shell thickness in the expanded state and are concerned that the number of destroyed microspheres will be excessive. It has been considered impossible until now. For this purpose, a hollow gear toothed inside a planetary gear extruder is at a temperature sufficient to initiate and continue its expansion as long as the polymer composition containing the microspheres is in contact with the hollow gear. Raised to a high enough temperature to reach. At the same time, the externally toothed sun gear is sufficiently low so that the polymer composition containing the microspheres does not reach a temperature sufficient to initiate or continue its expansion as long as it is in contact with the sun gear. Should be lowered to temperature.

  The composition temperature must be so high that the microspheres are inevitably expanded further, even for later expulsion of residual gases such as air, residual solvent vapors, residual monomers and water vapor for other purposes. And the pressure applied to it must be low, and the process conditions during mixing in the planetary gear extruder (especially the cylinder temperature, the center spindle temperature, the rotational speed, the filling degree and the pressure) are the most sophisticated laboratory conditions The technically practical and average expansion capacity obtained by achieving about three-quarters of the maximum volume that can be achieved at is selected such that it is completely used up at the end of mixing.

  Thus, depending on the type of microspheres used at that foaming temperature, it is possible to use a temperature profile in the radial and longitudinal directions during mixing such that foaming begins at least during mixing. The present inventor explains the surprising effect, i.e. the fact that the contact between the planetary gear and the hollow gear is particularly gentle, even if the microspheres begin to expand during mixing without damage. . Compared to the two outer teeth that mesh with each other, the planetary gear teeth gradually and gently fit into the gap between the teeth of the hollow gear, especially at the milder shear peak, and penetrated deepest After that, pull out gently as well. The same applies to the teeth of the hollow gear that comes out after fitting into the gap between the teeth of the planetary gear.

  Furthermore, the inventor presumes that the meshing of the planetary gears with the sun gear is relatively rough and therefore rarely has a detrimental effect on the microspheres because the composition to be mixed in this contact zone. The article is at least in the case of the acrylate and acrylate-methacrylate adhesive compositions to be tested, as far as this purpose is concerned, since the in-situ temperature is relatively low, the degree of adhesion is low, and therefore there is also a composition that stagnates There are few. In addition, this contact should not be compared with a twin screw extruder that rotates together with respect to the height of the shear peak, but rotates counterclockwise and therefore meshes with each other in a radial plane. It should only be compared with a twin screw extruder that is not visibly slippery (which is unusual with the exception of PVC processing). The tendency of clogging that occurs in oppositely rotating extruders is not observed in the case of planetary gear extruders (the inventor assumes that there is no inflexible enclosure between planetary gears and sun gears). Inadequate mixing, which usually seems disappointing, does not occur in combination with the non-uniform temperature profile according to the invention in a plane perpendicular to the transport direction of the mixer.

  The easier achievement of uniform mixing is particularly evident when the temperature difference between the hotter hollow gear and the cooler sun gear is at least 50 ° C. A temperature difference in the range of 65 ° C. to 90 ° C. is particularly preferred, especially since the onset of expansion can be controlled particularly reliably during mixing. On the other hand, higher temperature differences have been found to be unnecessary for the effect to be achieved, leading to unnecessary expenditure of money for unnecessarily strong heating and especially unnecessarily powerful cooling. It just means.

  Accepting the additional expense for cooling and heating, the present invention allows for a particularly high homogeneity of the mixture, and in a preferred embodiment of the invention a particularly precise control of the degree of expansion, and in particular A particularly early onset of expansion is possible with a particularly low proportion of broken microspheres. An earlier onset of inflation also allows for an earlier end of inflation. This not only has a cost advantage, but also allows the mold extrusion mold to pass at lower temperatures, with the added benefit of lower dimensional tolerances and a smoother surface in the final product. Without additional smoothing means, for example ultra-smooth backing and / or subsequent stratification by calendering, perhaps only after application of backing, less than 12 μm to peaks and valleys, up to 5 μm with special care Is achieved on the extrudate.

  Easier and improved mixing based on temperature non-uniformity according to the present invention is not only for microspheres due to the lower mechanical stress and lower thermal stress as a whole, but also as intended. It is also gentle on polymers. Thus, polymer degradation remains low. Cost advantages are achieved by the ability to stop mixing and expansion more quickly, and the quality advantages achieved are more important than the cost disadvantages based on higher heating and cooling costs.

  The matrix surrounding the microspheres in the product according to the invention essentially contains a polymer. If the matrix is to be self-adhesive, it is preferably also acrylate and / or methacrylate and / or polyolefin and / or natural rubber and / or styrene-butadiene rubber and preferably also one or more tack-promoting resins. contains. It is also possible to use thermoplastic elastomers such as styrene block copolymers, such as styrene-isoprene-styrene (SIS) and styrene-butadiene-styrene (SBS) grades.

As the adhesion promoting resin, it is possible to use an oligomer compound and a low polymerization compound having a number average molecular weight M _{n of} up to 5000 g / mol. Possible are, inter alia, pinene resins, indene resins and rosin resins, disproportionated, hydrogenated, polymerized, esterified derivatives and their salts, aliphatic hydrocarbon resins and aromatic carbonization. Hydrogen resins, terpene resins and terpene-phenol resins and also C5-, C9- and other hydrocarbon resins, each possible on their own or in combination with one another. All resins soluble in the polymer composition, for example, all aliphatic hydrocarbon resins, aromatic hydrocarbon resins, alkyl aromatic hydrocarbon resins, and hydrocarbon resins based on pure monomers, hydrogenated hydrocarbon resins Functional hydrocarbon resins and natural resins can be used particularly advantageously. Preferred terpene-phenol resins are Dertophene T105 and Dertophene T110, and a preferred hydrogenated rosin derivative is Foral 85. The resin ratio should be as low as possible in view of the time to withstand the shear that can be achieved, and as high as necessary in view of the tack and vibration damping required for use.

  In addition, plasticizers such as low molecular weight polyacrylates, polymethacrylates, phthalates and polyphosphoric acids can be added to further increase the deformability, impact toughness and vibration damping capability, which is often slightly tacky Accompanied by an increase.

  Cross-linking of the matrix material is also advantageous for most applications. Even if such cross-linking is advantageously carried out only at the end of the process, it must be taken into account in the selection of the material used initially. Thus, when using natural rubber, isoprene rubber or SBR rubber, and / or preferably when first using other polymers, the monomers used in the production of the polymers may later be cross-linked together. When incorporating functional groups that can be made, it may be useful to add a cross-linking agent such as sulfur or peroxide. What is possible here is in particular an olefinically unsaturated monomer having a functional group capable of reacting with an epoxide group. In this case, monomers having functional groups from the following classes are preferred. That is, they are a hydroxy group, a carboxy group, a sulfonic acid group, a phosphonic acid group, an acid anhydride, an epoxide, and an amine. Particularly preferred examples of such monomers are 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, itaconic acid, maleic anhydride, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, 6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate and glycidyl methacrylate.

  As is known per se, the crosslinking reaction can be initiated by the introduction of energy, ie UV irradiation, electron beam or heating. The crosslinking initiator to be mixed into the matrix should be selected according to the desired type of energy. If a composition that is colored and therefore has little or no transparency is to be processed, or if it is to be produced with a layer thickness of more than about 160 μm, it is preferred to produce the product, so that the crosslinking reaction Should be initiated with heat, where the type of microspheres used, the temperature profile and the initiator are used wherever crosslinking occurs in the mold, calendering roller and / or extrusion mold. The locations where they are added should also preferably be matched to each other so that crosslinking does not begin much earlier than molding. Suitable heat activatable crosslinking agents for particularly preferred acrylates and methacrylates are, in particular, isocyanate and epoxide compounds.

  Accelerators and / or retarders for the crosslinking reaction can also be advantageously added, in particular planetary gears which are preferably used even during mixing when the crosslinking agent is added at the start of the extruder Assuming that the outermost radial region of the extruder is exposed to a temperature at which crosslinking can begin, minimize the expense of mixing with respect to time and equipment. As an alternative to or in addition to the use of retarders, obstacles or steric hindrances can be incorporated into the cross-linking isocyanate, for example by alcohols, phenol derivatives or amines. In particular, if a little yellowing tendency is not a problem in the application to be provided, this excess can be dealt with by a small amount of cross-linking accelerator, e.g. amine, than is required for the above purpose in the mixture. It is preferable to use a little more retarder. In general, this makes the cross-linking progress over time less sensitive to variations that can never be avoided in the process sequence, thereby further reducing variations in product quality.

  If the planetary gear extruder is divided into modules and the crosslinker must be thermally activated and can be distributed sufficiently homogeneously with a short mixing distance, the crosslinker is placed behind the planetary gear extruder. Is preferably added to one or more downstream extruders because the process conditions particularly advantageous for mixing and foaming are related to the crosslinking agent and its premature and / or excessively severe crosslinking. This is because it is not necessary to consider the increase in viscosity.

  With respect to the arrangement of each hollow gear and the planet gears meshed within it, each module of a multi-module planetary gear extruder looks like an independent (one module) planetary gear extruder, but a single central spindle is Operates with modules. In contrast to four one-module planetary gear extruders arranged in series (a motor and gearbox are required for each of the four central spindles), a four-module planetary gear extruder has a unique motor and unique All you need is a gearbox. Although they must be made correspondingly stronger, a single strong drive provides better efficiency than the four weaker drives because the risk of breakage is reduced and maintenance costs are reduced.

The polymer foam preferably contains at least 25% by weight, based on the total weight of the polymer foam, of an acrylic polymer, either polyacrylate or polymethacrylate or poly (acrylate-co-methacrylate) or copolymer, which This is thought to be due to the monomer composition of
(A) Formula CH ₂ = C (R ′) (COOR ″),
Where R ′ = H or CH ₃ and R ″ is an alkyl radical having 4 to 14 carbon atoms.
Acrylic esters and / or methacrylic esters of
(B) a relatively small amount of an olefinically unsaturated monomer having a functional group reactive with the crosslinker material or part of the crosslinker material specifically mentioned in the second paragraph;
(C) acrylates and / or methacrylates other than (a) and / or (d) optionally further monomers that are olefinically unsaturated and can be copolymerized with component (a), optionally in relatively small amounts.

  The term “in a relatively small amount” means an addition in which the weight ratio of the added component is less than a quarter of component (a).

  For purposes of this patent application, compounds in group (a) are referred to as “acrylic monomers”. It is preferable to use an acrylic monomer whose alkyl group contains 4 to 9 carbon atoms. Examples of such monomers are 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, n-nonyl methacrylate, isobutyl acrylate, isobutyl methacrylate, isooctyl acrylate, isooctyl methacrylate, and branched isomers thereof such as 2-ethylhexyl acrylate and 2-ethylhexyl Methacrylate.

  Furthermore, group (a) also includes dodecyl methacrylate, lauryl acrylate, n-undecyl acrylate, n-tridecyl acrylate, sec-butyl acrylate, tert-butyl acrylate, isodecyl acrylate, It is possible to form a copolymer.

For polymers containing component (c) and / or (d) it is possible in principle to use all vinyl-functionalized compounds which can be copolymerized with component (a) and / or component (b) It is. These monomers preferably also help to adjust the properties of the resulting polymer foam. The following monomers for component (c) can be mentioned as examples:
Methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate, ethyl methacrylate, benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenyl methacrylate, isobornyl acrylate, isobornyl methacrylate, t-butylphenyl acrylate, t-butylphenyl methacrylate, stearyl Acrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentyl methacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethyl methacrylate, 2-butoxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyladamantyl acrylate, 4 -Cumylphenyl meta Relate, cyanoethyl acrylate, cyanoethyl methacrylate, 4-biphenyl acrylate, 4-biphenyl methacrylate, 2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofurfuryl acrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate 2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, methyl 3-methoxyacrylate, 3-methoxybutyl acrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycol methacrylate, ethylene glycol acrylate, ethylene glycol Nomethyl acrylate, methoxy-polyethylene glycol methacrylate 350, methoxy-polyethylene glycol methacrylate 500, propylene glycol monomethacrylate, butoxydiethylene glycol methacrylate, ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate, octafluoropentyl methacrylate, 2,2,2-tri Fluoroethyl methacrylate, 1,1,1,3,3,3-hexafluoroisopropyl acrylate, 1,1,1,3,3,3-hexafluoroisopropyl methacrylate, 2,2,3,3,3-pentafluoro Propyl methacrylate, 2,2,3,4,4,4-hexafluorobutyl methacrylate, 2,2,3,3,4,4,4-heptaful Orobutyl acrylate, 2,2,3,3,4,4,4-heptafluorobutyl methacrylate, 2,2,3,3,4,4,5,5,6,6,7,7,8,8 , 8-pentadecafluorooctyl methacrylate or macromonomer, such as 2-polystyrene-ethyl methacrylate (molecular weight Mw 4000-13000 g / mol), poly (methyl methacrylate) -ethyl methacrylate (Mw 2000-8000 g / mol), and the like.

Examples of the component (d) include the following monomers.
Dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide, N- (1-methylundecyl) acrylamide, N- (n-butoxymethyl) acrylamide, N- (butoxymethyl) methacrylamide, N- (ethoxymethyl) acrylamide, N -(N-octadecyl) acrylamide and also N, N-dialkyl-substituted amides such as N, N-dimethylacrylamide, N, N-dimethylmethacrylamide, etc., N-benzylacrylamide, N-isopropylacrylamide, N-tertbutylacrylamide N-tert octyl acrylamide, N-methylol acrylamide, N-methylol methacrylamide, acrylonitrile, methacrylonitrile, vinyl ether such as vinyl methyl ether , Ethyl vinyl ether, vinyl isobutyl ether, etc., vinyl esters such as vinyl acetate, vinyl chloride, vinyl halide, vinylidene chloride, vinylidene halide, vinyl pyridine, 4-vinyl pyridine, N-vinyl phthalimide, N-vinyl lactam, N -Vinylpyrrolidone, styrene, a-methylstyrene and p-methylstyrene, a-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene, 3,4-dimethoxystyrene.

  The monomers of component (c) can also be advantageously selected such that they contain functional groups that are useful for subsequent irradiation-chemical crosslinking (eg using electron beam, UV). Suitable copolymerizable photoinitiators are, for example, benzophenone derivatives functionalized with benzoin acrylate and acrylate. Monomers useful for electron beam crosslinking are, for example, tetrahydrofurfuryl acrylate, N-tert-butylacrylamide and allyl acrylate.

  It is particularly advantageous that the polymer forming the matrix also contains acrylic acid and / or methacrylic acid in copolymerized form.

  In order to preferably use the polymer foam as a pressure sensitive adhesive, the ratio of each component (a), (b), (c) and (d) is such that the polymerization product preferably has a glass transition temperature of ≦ 15 ° C. Selected (with DMA infrequently). For this purpose, the monomer of component (a) in a proportion of 45 to 99% by weight, the monomer of component (b) in the proportion of 1 to 15% by weight and the monomers of components (c) and (d) It is advantageous to use in proportions of 0 to 40% by weight, the amounts given here being based on the monomer mixture of the “base polymer”, ie any additive such as a resin is added to the finished polymer. Not.

In order to use the polymer foam as a hot melt adhesive, i.e. a material that becomes tacky only as a result of heating, the ratio of each component (a), (b), (c) and optional (d) is Preferably, the copolymer is selected such that it has a glass transition temperature (T _G ) in the range of 15 ° C. to 100 ° C., more preferably 30 ° C. to 80 ° C. and particularly preferably 40 ° C. to 60 ° C.

The matrix can also contain fillers such as titanium oxide, zinc oxide, carbon black, chalk (= calcium carbonate, CaCO ₃ ) and other additives such as anti-aging agents, flame retardants, fungicides and the like. . In addition, in addition to expandable microspheres, i.e. those having a polymer shell and a blowing agent in it, preferably allowing the volume to increase by evaporation, non-expandable microspheres, e.g. hollow Glass microspheres can be used.

  In general, the above components, which are less sensitive than the microspheres to the temperature, pressure and shear stresses that occur during the process, are first mixed, optionally to the microspheres that appear to be more sensitive to them. The heat sensitive crosslinking agent and any crosslinking retarder are later mixed together. However, this kind of gentle processing of the microspheres does not save the manufacturer's budget because the total mixing time and the required total length of the mixer are rather long, and in particular a relatively long machine. Matrix polymers that are exposed to mechanical and thermal stress are not saved.

  After the description of the principle of the method of the invention and the important embodiments, an apparatus suitable for the purpose will now be described.

  The hollow gear of the planetary gear extruder is also referred to as “toothed cylindrical part” or “cylindrical part” or “hollow roller” or “roller casing”, “internal toothed cylinder”, and the like, and has various names. Regardless of the name used for that, its invariant nature serves both heating and cooling. In order to heat the hollow gear, especially as described in detail earlier, it is preferred to process any type of acrylate as the base polymer, and sufficient hot water or steam in any case other steps Hot water or steam, otherwise heating wire should be used. In order to cool the hollow gear, as described in detail earlier, it is particularly preferred mainly for processing polyolefin-based compositions, so it operates in series according to the Linde principle, preferably a cooling device connected in series. Cold water flowing through the cooling device and the circulation pump should be circulated through the liquid channel in the cylinder.

  In accordance with the present invention, the temperature of the sun gear (= sun roller = center spindle) should also be able to be effectively controlled in order to create a temperature gradient in the radial plane of the extruder. In particular, in order to process any type of acrylate as a base polymer, heat should be recovered from the sun gear as described in detail above. For this purpose, a cooling device, preferably a cold water channel, should be placed therein. These chilled water channels should preferably be connected to an external cooling device operating according to the Linde principle.

  In the control device for cooling the hollow gear (described first) or the sun gear (last described), the measured temperature variation advantageously has a frequency range, and the infrequent temperature variation is the driving of the cooling device. The frequency fluctuations are made uniform by affecting the force, and the frequent frequency fluctuations are made uniform by affecting the driving force of the circulation pump between the cooling device and the hollow gear or the sun gear, which This is because the power of the pump can be adjusted with a response with a smaller delay than the power of the compressor in the cooling device.

Return to the process:
On the way to the present invention, the inventor makes it more difficult to improve the degree of uniformity achieved to a certain point in the method, the higher the degree of uniformity achieved so far. Recognized that Therefore, going from “Unsatisfactory” to “Acceptable” is easier than “Acceptable” to “Satisfied” step, which is progressive, leading to the evaluation of “Excellent” It is easier than further steps. The inventor found that the only thing important during mixing was at different temperatures, whether it was a molecule as in the case of polymers and a piece of resin or the same material as in the case of microspheres. It has also been recognized that there is effectively a uniform distribution of material, eg, microspheres, rather than a uniform distribution of individual members. Based on this, the present inventor developed the idea of mixing materials at very different temperatures. The force that drives the increased natural temperature equalization thereby also promotes mixing of the materials. This advantage is particularly noticeable in the mixing of microspheres because they are huge compared to the size of the polymer molecules.

  The heating / cooling difference according to the invention is useful in the cross-sectional plane at the early confluence where the flow to be mixed has reached, but it is even more important in the last module provided for mixing. The temperature difference between the hot and cold components is therefore preferably maximum there. The most important objective of the present invention is to reduce mechanical and thermal stress on the matrix polymer, so that the cold components are particularly significantly cooled in the zone of the extruder where the final mixing occurs and the hot components It seems advisable not to heat that particularly significantly.

  In a non-uniform temperature zone configuration preferred for processing all types of acrylates to be foamed, i.e., for a central spindle that is significantly cooler compared to the hollow gear, the inventors have heated the hollow gear simultaneously. It was also concluded that the cooling of the sun roller (= sun gear), which increases the mixing force, is particularly important in the final stage of mixing (as seen in the vertical plane of the mixer). Therefore, the coolant preferably flows in the direction opposite to the polymer transport direction inside the sun roller.

  One further embodiment of the method of the invention is characterized in that the expandable microspheres are first suspended in water and then introduced. In combination with this suspension (ie, not dry microspheres), the subsequent expansion of the microspheres that were first introduced into the matrix-forming polymer composition and then mixed was directed by the microsphere manufacturer. It is advantageously started at a temperature below the expansion start temperature. According to new recognition, this manufacturer's data applies only to dry microspheres.

  Thus, pre-suspending the microspheres in water not only reduces the risk of dust formation and explosion at the location where the microspheres are fed, but especially if it contains polyacrylonitrile rubber, It also acts as a plasticizer. Although suspensions of expandable microspheres in water are known (such pastes can be purchased in the finished form from Akzo Nobel under the trade name Expandel (C)), the microspheres of this suspension step There is no known teaching based on this recognition that the effect on expansion behavior and expansion should begin below the expansion start temperature. Even lower temperature levels during expansion in more advanced processes save even more matrix polymer.

  The inventor believes that the suspension in water introduces water into the mixture and that, apart from the water that diffuses in and through the microsphere shell, no individual water droplets are effectively formed in the mixture. Instead, it has been observed that the surface of the microspheres will get wet with water. This has been successful in the case of microspheres having a shell consisting at least essentially of polyacrylonitrile. The inventors expect that this effect will be successful for other types of microspheres as long as the polarity of the shell material matches that of water. This humidification of the microsphere surface, as the inventors have discovered, causes a reduction in lubrication and adhesion between the microspheres and the matrix material, which further facilitates mixing and at the same time shear stress on the microspheres during mixing. Decrease.

  Neither the water-microsphere emulsion produced in-house nor the purchased finished emulsion suffers from the problem of mixing and separation when left standing because the specific gravity of water and microspheres is not the same. As the inventor has confirmed in careful studies, such mixed separation is responsible for the low frequency disturbances over the length of the extrudate in the introduction of microspheres, so that they are now compensated by mixing. Could not be reflected as density variation in the final product. The obvious solution is to continuously stir the storage emulsion, either too low to eliminate this defect or have caused an excessively high proportion of microspheres destroyed by this stirring. Happened with a stirring force of. In the case of a composition produced in black at least in any case, the inventor should change from a binary material system to a ternary material system by introducing carbon black as a third material. Invented a simple but effective theory. We have found that it is particularly effective to first emulsify carbon black in water to form a sufficiently fluid black paste, then add microspheres and then obtain a thick black paste.

  In order to obtain the maximum possible strength in the finished extruded product, the water content of the mixture, preferably the self-adhesive composition, is again adjusted at some point after the introduction of the aqueous carbon black-microsphere suspension. Should be reduced. This is preferably done only after a sufficient uniform distribution of the microspheres in the matrix-forming composition is achieved in order to keep the lubrication effect of water for a long time and use this effect as best as possible. The Therefore, application of sub-atmospheric pressure to force water removal is preferably performed only at a later stage in the processing of the composition. Water removal can be planned in the final module of the planetary gear extruder, but it can also be arranged in further downstream equipment, such as a single screw extruder.

  Any arrangement of water removal should apply sub-atmospheric pressure to drive this removal strongly. To force further water removal, temperatures close to or slightly above 100 ° C are also advantageous, and this preferred feature is selected by the type of microspheres, particularly so that the onset of expansion exceeds 100 ° C. Can be used easily.

  The microspheres are softened by emulsification in water as disclosed herein and before the sixth paragraph, thus lowering their expansion start temperature so that at least a significant portion of the expansion is only for dry microspheres. The idea of carrying out at a temperature below the expansion start temperature indicated in advance by can also be realized independently, i.e. independently of any non-uniformity in the temperature range in the diversity according to the main invention of this patent application. The same is a preferred embodiment of this secondary idea, i.e. the composition to be extruded first after carbon black is emulsified in water and then microspheres are introduced into the emulsion at the end of mixing or after mixing. This also applies to embodiments in which only at least a large part of the water introduced together with the emulsion is removed again.

  However, when water removal is performed in combination with a non-uniform temperature region according to the main invention, at least one of the two boundary surfaces of the mixing space should have a temperature close to or above 100 ° C. In combination with carrying out the process in a planetary gear extruder and in combination with acrylate and / or methacrylate as the base polymer of the composition to be processed, at least the hollow gear is close to 100 ° C. in the water removal zone Or should have a temperature above that. The special advantage of dewatering at a hollow gear temperature just below 100 ° C., preferably about 95 ° C., is that the boiling point only exceeds in the composition to be dehydrated as a result of the additionally introduced kneading heat. It is that. However, this kneading also ensures that large voids of water vapor are not formed that can impair the quality of the final product. If this kneading does not take place, either due to malfunction or because the person managing the device takes a break, the evaporation does not proceed in an uncontrolled manner. Therefore, the formation of dangerous vapor pressure is automatically prevented.

  Even if the hot boundary surface remains below 100 ° C., if the acrylate and / or methacrylate central spindle is not dehydrated or at least not overcooled in the final module of the planetary gear extruder, the other surface is dewatered. It is advantageous to do so. Thus, a very non-uniform temperature distribution in the plane of the cross-section, which was previously very advantageous in the mixing module, is therefore no longer preferred in the dehydration step. As a further solution to this problem, it is preferred to form a “cooling” channel in the central spindle in this dewatering area that is large enough so that its inside can be backed with a thermal insulation sleeve. This strategy achieves two advantages at the same time. That is, firstly, preferably where the coolant flowing from back to front does not cool, the central spindle is hardly cooled, and secondly, the coolant is hardly heated while passing through the dehydration and degassing areas. Since it is not exposed, the central spindle is particularly well cooled as a result of the inner wall of the cooling channel being left bare in the mixing zone located before this dewatering and degassing zone. The insulating sleeve is advantageously composed of a polymer tube of syntactic foam type. The high air bubble content therein guarantees good insulation.

  Similar conditions apply when using other types of extruders, as are preferred for processing of polyolefin-based compositions, and similar reverses apply in the reverse temperature range. However, in the case of the configuration of temperature non-uniformity in the preferred mixing module for mixing polyolefin-based compositions containing expandable microspheres, ie in the case of a hot sun spindle and a cold hollow gear, in the dehydration and degassing module The widespread problem of this non-uniformity is that the cooling channels of the various modules can be controlled separately, making it very easy and easy to circulate hot and non-cold water in the corresponding channels. Can be achieved accurately.

  Because the microspheres do not expand into this dewatering, or at least do not expand too much, a type of microsphere with an onset expansion temperature exceeding 100 ° C. even in suspension is not suitable for this embodiment of the invention. Based on the inventors' experience with microspheres that are particularly useful and whose shell consists essentially of polyacrylonitrile, an expansion onset temperature as high as 25 ° C. would be expected for a dry material.

The self-adhesive tape is preferably manufactured by the method described above and its preferred embodiments. For this purpose, a polymer composition containing microspheres is
Applied in a single layer on the support of the single-sided self-adhesive tape to be formed, or applied in a single layer on each of both sides of the support of the double-sided self-adhesive tape to be formed, or Whether applied in a single layer on the backing and then laminating the composite with the composite after the first mirror coating or forming itself into a self-adhesive double-sided tape without support Either.

Regarding equipment suitable for carrying out the process,
In order to carry out the method according to the invention in a planetary gear extruder using a temperature gradient from a hot hollow gear to a cooler sun gear, the hollow gear includes a planetary gear extruder that includes a heating device. It is advantageous. A much shorter and more reproducible starting behavior of the device compared to a planetary gear extruder, where heat is supplied only by the introduced kneading operation, is achieved when this does not have to be run all day Is done. In addition, the magnitude of the temperature gradient according to the invention can be set within a wider range and with higher accuracy.

  In order to achieve a preferred form of temperature gradient, ie a temperature gradient from a hot hollow gear to a cooler sun gear, it is absolutely necessary that the sun gear is equipped with a cooling device. However, a reverse temperature gradient can be created without a cooling device in the sun gear.

  In order to carry out the method of the invention using the preferred suspension of microspheres in water, they are introduced and then downstream of a single module or multi-module planetary gear extruder before removing the water. It is advantageous to provide a production device with a sub-atmospheric pressure zone upstream of the first or only molding device (extrusion mold and / or calendering roller). Water removal occurs satisfactorily, especially in sub-atmospheric pressure zones, especially as water vapor.

About products:
The present invention also encompasses a self-adhesive tape containing a foamed self-adhesive composition or consisting solely of the self-adhesive composition produced by the method of the present invention. These self-adhesive tapes have in their self-adhesive compositions a molar mass distribution that is particularly close to the molar mass distribution of the polymer used at the start of the process. Thus, the maximum molar mass decrease and the low molar mass increase are particularly small. Due to the milder polymer treatment during the production of the self-adhesive tape according to the invention, it is expected that this tape will be strong for a long time, i.e. fatigue failure will only occur much later.

  Furthermore, the self-adhesive tape according to the invention has a particularly smooth surface and is self-adhesive produced only by extrusion, depending on the carefulness of operation and the purity of the surrounding air, ie the extrusion mold. The tape achieves a peak-to-valley average height in the range of 12-2 μm. These self-adhesive tapes therefore adhere easier than expected from the composition rheological data alone. This can be used to allow for the setting of a higher degree of cross-linking, and to achieve a higher shear stabilization time, the secondary effects that reduce its stickiness are acceptable to a considerable extent. .

  Due to the particularly high fatigue strength of the self-adhesive composition produced according to the present invention, when the self-adhesive layer (or layers) is produced from a single layer of self-adhesive processed according to the present invention, The composition is sufficient to produce most self-adhesive tapes.

FIG. 1 is a diagram schematically showing an apparatus (planetary gear extruder 1) according to the present invention.

  The invention is described below with the help of preferred examples.

Initially, the base polymer was prepared by free radical polymerization in a conventional reactor. For this purpose, what is loaded into the reactor is
54.4 kg of 2-ethylhexyl acrylate,
20.0 kg of methyl acrylate,
5.6 kg acrylic acid and 53.3 kg acetone / isopropanol solvent mixture (94: 6).

  After stirring for 45 minutes, the reactor was heated to 58 ° C. under an atmosphere enriched with nitrogen gas to reduce the risk of fire and explosion, and DuPont's Vazo® 67, ie 2 40 g of 2,2'-azobis (2-methylbutyronitrile) was added. Subsequently, the external heating bath was heated to 75 ° C. and the reaction was carried out by maintaining this external temperature. After 1 hour, an additional 40 g of Vazo 67 was added, and after another 4 hours, the solution was diluted once more with another 10 kg of solvent (again acetone / isopropanol mixture (94: 6)) to help transfer residual monomer, Increased the degree of polymerization and thus decreased the residual monomer content. After another 5 hours and after another 7 hours, 120 g of Akzo Nobel's PerkadoxC (C) 16, ie, bis (4-tert-butylcyclohexyl) peroxydicarbonate, was additionally introduced, and the polymerization reaction proceeded. Kept. The polymerization was stopped after a further 5 hours, ie after a total reaction time of 22 hours. By this time, a solids content of 55.9% had been obtained in the reactor.

The polyacrylate thus obtained was measured in the laboratory for in-house quality control. For this purpose, the residual solvent content of a small sample was reduced to less than 1% in a vacuum dryer, after which the polymer was dissolved in 99% by weight of toluene (= methylbenzene according to IUPAC nomenclature). The K-value was then measured by the Fikenscher method, ie using a Vogel-Ossag viscometer maintained at 25 ° C. The K-value measured in this way is 58.8, which serves as a measure of the average molecular weight of the polymer material (see also Polymer, 1967, No. 8, page 381, ff. (Non-patent Document 1)). ). Average molecular weight _M w = _746,000g / mol, polydispersity _{D (M w / M n)} 8.9 and a static glass transition temperature _T g -35.6 ° C. was also measured.

  This acrylate copolymer, which serves as the substrate, was then concentrated to a residual solvent content of less than 0.3 weight percent in a single screw extruder.

  In addition to the base polymer described above, microspheres were manufactured. For this purpose, Akzo Nobel's Expandel 051DU40 microspheres (with unexpanded diameters in the range of 10-16 μm) were introduced into an aqueous carbon black paste (Levans Schwartz N-LF, Lanxess Deutschland GmbH). The purchased Levanyl carbon black paste, according to the knowledge of those skilled in the art, contains 40% carbon black and 60% water. Carbon black in water stabilizes the three-component emulsion produced by adding microspheres to the carbon black paste from the beginning. As used herein, “stabilization” means physical stabilization, that is, prevention of separation of the three components due to their different densities. Thanks to the high water content in any case of the purchased carbon black paste, no additional water may be added to it before mixing the microspheres. 69.5 parts by weight of Expandel 051DU40 microspheres were added to 100 parts by weight of Levanyl carbon black paste. Thus, the paste thus produced contained 23.6% carbon black, 35.4% water and 41% microspheres.

  In order to obtain the benefit of a favorable reduction in the temperature required for the onset of expansion, in a further embodiment of the invention, this paste containing microspheres is first stored at room temperature. The desired effect can be detected after only a few minutes of storage time, but to the extent that this desired effect is possible to the maximum, and in particular the constancy over storage time, and therefore quantitatively very easy and reliable reproduction A storage time of at least 12 hours is desirable to achieve sex. After this time, the effect of lowering the expansion start temperature asymptotically approaches its maximum at t → ∞, and further storage time rarely increases this effect.

  Only after the plasticizing effect of water on microsphere shells containing essentially nitrile rubber has been established, this paste containing carbon black, water and microspheres in a base polymer, to 100 parts by weight of polymer In an amount of 2.44 parts by weight. This paste was introduced into the supply shaft of the planetary gear extruder.

  In addition, the following were introduced into the planetary gear extruder at a weight ratio of 100 phr to the base polymer at this feed shaft.

  Polypox R16 is marketed by Dow Chemical, functions as a crosslinker, and is pentaerythritol polyglycidyl ether according to IUPAC.

  Epikure 925 is commercially available from Hexion Specialty and also serves as a crosslinker, and is triethylenetetramine according to IUPAC.

  When the total is 100 w%, the paste is divided into its components as follows.

  An Entex 4-module planetary gear extruder 1 is used to carry out this example of the method of the present invention. In front of the first module, there is a take-up area, in which the feed hopper feeds directly into the central spindle 5, in which case the planetary gear 6 has not yet rotated around the central spindle 5.

  Both the acrylate polymer and Dertophene T110 resin are metered into the feed shaft gravimetrically. It has been found advantageous to preheat the resin to 150 ° C. in order to further improve the efficiency of mixing. The resin is advantageously supplied as an extrudate from an upstream single screw extruder.

  The acrylate polymer can be introduced as pellets. However, for economic reasons, not for technical reasons (the polymer was produced in the inventor's own manufacturing facility), this polymer was also fed from other extruders in the form of extrudates in this example. Therefore, the pelletizing step could be omitted. In the most reasonable way of carrying out the process, this other extruder is identical to the concentrating extruder at the end of the polymer production process and produces a continuous production. It has been found to be particularly advantageous to feed the extrudate of acrylate copolymer at 140 ° C.

  Internally, after this intake region where the cooling channel 5.1 passes through the central spindle 5, the coolant is heated to about 41 ° C. to 44 ° C. in the central spindle, with cooling to 50 ° C. The channel through which the water is introduced penetrates the cylindrical part and the supply shaft, and then the composition travels in the axial direction of the oblique teeth of the continuous central spindle 5, so that the first gear of the planetary gear extruder 1. Proceed into the module. Both the hollow gear and the center spindle are cooled in this first module, not only to remove the heat introduced here by kneading, but also to reduce the temperature of the composition.

  Each of the four modules of the equipment used was approximately 1.1 m long. The set of pitch circle diameters inside the teeth of the hollow gear was about 550 mm, and the pitch circle diameter of the planetary gear was about 50 mm. The central spindle was rotated at 30 rpm.

  The figure shows schematically the cross section through the first module (= module 1) of the planetary gear extruder and the temperature of the temperature-controlled water there in the upper left.

  In the direction opposite to the polymer transport direction, the water cooled to 50 ° C. is pumped into the cooling channel 7.1 of the cylindrical part 7 (= internal toothed hollow gear = hollow roller = roller cylinder) At the beginning, it is removed again at about 55 ° C., transported into the first cooling device, where it is cooled again to 50 ° C. and reintroduced into the cylindrical part 7 at the end of this first module. The drawing shows the introduction temperature in each case of the temperature control medium.

  The central spindle 5 is cooled by the cooling channel 5.1. Unlike the temperature control channel 7.1 of the individual cylinder 7 for each module, the cooling channel 5.1 passes through the central spindle 5 without obstruction because the central spindle 5 itself is unobstructed. . For this reason, it is possible to directly control only the temperature of the coolant at the inlet, at the end, in this case the end of the fourth module. At this back point, spindle cooling water was introduced at 30 ° C. It goes to the end of the first module at 37 ° C., exits at 41 ° C., flows from there to the above intake region, and is further heated to about 44 ° C., as shown by intermediate measurements and model calculations. And then finally flows from there to the second cooling device, where it is cooled again to 30 ° C. and then re-passes through the sliding seal into the cooling channel 5.1 at the end of the fourth module. be introduced.

  The takeover point from one module to the next does not have a planetary gear extending through them. For this reason, further materials can be introduced particularly easily at these takeover points. A three-component paste containing water, carbon black and microspheres is weighed gravimetrically from the first module to the second module at the takeover point.

  The figure schematically shows the cross section through the second module (= module 2) of the planetary gear extruder 1 in the upper right and the temperature of the temperature-controlled water there. 115 ° C. water (ie pressure above atmospheric pressure) is introduced into the channel 7.1 of the cylindrical part of the module. Here, this water has a heating action but no cooling action, like the temperature control water of the cylindrical portion in the intake region and the first module. The cooling water of the center spindle passes over the boundary between the third module and the second module at about 34 ° C. and leaves the second module at about 37 ° C. in the direction of the first module.

  Since the metal used for the cylinder and the spindle has a high thermal conductivity, the surface temperature of each is close to the temperature of the temperature-controlled water used in each case. Inside the cylinder 7, the heat transfer calculation shows an average surface temperature of about 112 ° C. in this second module. On the outer surface of the central spindle 5, the heat transfer calculation shows an average surface temperature of 38 ° C. in this module. The temperature difference between the two surfaces is therefore about 74 ° C. This temperature difference results in a substantially non-uniform temperature region according to the invention in the plane of the cross section through this second module of the planetary gear extruder.

  The planetary roller 6 not shown in the figure for the sake of clarity exhibits a temperature between these extreme conditions. According to the model calculation for heat transfer, the planetary gear has a temperature of about 80 ° C. on the side facing the hollow gear 7 and a temperature of about 79 ° C. on the side facing the sun gear.

  These temperature conditions result in a thin layer in which the composition has expanded, which is far from the carbon distribution in the Damascus steel blade. The expansion of the microspheres is carried out in the hollow gear 7 between the planetary gear 6 and the hollow gear 7 but only there in a layer sufficiently close to the surface of the hollow gear. Nevertheless, surprisingly, the inventor found that the entire composition expanded uniformly and perfectly at the edges, and that the inventor mixed the amount of parts that had already expanded with the amount of parts that had not yet expanded. This is explained by the exceptionally good mixing performance based on the large temperature difference that also leads to Therefore, the previously continuous expansion process is in this case divided into a plurality of expansion parts in time and space.

  No additional points were introduced at the takeover point between the second and third modules. The corresponding lid remained closed.

  The figure shows schematically the cross section through the third module (= module 3) of the planetary gear extruder 1 and the temperature-controlled water temperature at this location in the lower left. Hot water is likewise introduced at 115 ° C. into the cylindrical channel 7.1 of this module. This water here has a smaller heating effect than in the second module. The cooling water of the center spindle passes over the boundary between the fourth module and the third module at about 32 ° C. and leaves the third module at about 34 ° C. toward the second module.

  Since the metal used for the cylindrical part and the spindle has a high thermal conductivity, the surface temperature of each metal is close to the temperature of the water of the respective temperature control. Inside the cylindrical part 7, the heat transfer calculation shows an average surface temperature of about 113 ° C. in this second module. On the outer surface of the central spindle 5, the heat transfer calculation shows an average surface temperature of 35 ° C. in this module. The temperature difference between the two surfaces is therefore about 78 ° C. This temperature difference is a slightly more non-uniform temperature region in the plane of the cross section through this third module than in the second module of the planetary gear extruder.

  Also in this third module, the planetary roller exhibits the extreme temperature described above. According to the model calculation for heat transfer, the planetary gear has a temperature of about 79 ° C. on the side facing the hollow gear and a temperature of about 78 ° C. on the side facing the sun gear.

  As a result of these temperature conditions, which are slightly more severe compared to the second module, expansion of the thin layer of the composition also occurs here. The expansion of the microspheres takes place in the hollow gear 7 between the planetary gear 6 and the hollow gear 7 but only there in a layer sufficiently close to the hollow gear surface.

  Easily incorporated but temperature sensitive crosslinkers Polypox R16 and Epikure 925 were weighed in and introduced at the takeover point from the third module to the fourth module (= module 4) .

  The figure shows, in the lower right, the section through the fourth module of the planetary gear extruder 1 (= module 4) and the temperature of the temperature-controlled water there. Water at 50 ° C. is introduced into the cylindrical channel 7.1 of the module and cooled. Central spindle cooling water enters one end at about 30 ° C. and passes across the boundary between the fourth and third modules at about 32 ° C.

  The considerable drop in process temperature in this module does not cause the microspheres to expand further and allows the vacuum to be used to expel air and water vapor. Also in this step, a good distribution of the two crosslinkers is achieved.

  Next, when the composition was passed through a single screw extruder heated / cooled in a conventional manner, the composition was reheated to the extrusion temperature and at the same time the pressure increased. The temperature had to be set just above the expansion start temperature of the microspheres in order to obtain a flow sufficiently prepared to pass through the extrusion mold, but because of the previously achieved expansion, Due to the combination of high pressure in this single screw extruder and reduced gas pressure in the microspheres, there was very little increase in expansion. The extruded longitudinal section shows a rarely smooth surface with an average peak-to-valley height of less than 12 μm.

  In a comparative experiment, if the very non-uniform temperature regions in the second and third modules of the planetary gear extruder were not provided, the uniformity was poor and the average peak-to-valley height was large. Thus, this high non-uniformity is considered to be a factor in the success achieved. If both the spindle temperature and the temperature of the hollow gear in the module exceeded the microsphere expansion onset temperature, which was reduced by the action of water, in some cases, good foam uniformity was not obtained. In contrast, if both temperatures were below the expansion start temperature, no foaming occurred.

  A list of reference signs is given as part of the description below.

DESCRIPTION OF SYMBOLS 1 Mixer, planetary gear extruder 2 Mixing space in mixer 1 3 Temperature T ₃ , first surface 4 serving as boundary of mixing space 2 Temperature T _{4 serving} as boundary of mixing space 2 Second surface 5 Planetary gear extruder central spindle = sun gear = sun roller 5.1 Cooling channel in 5 6 Planetary gear extruder planetary roller 7 Planetary gear extruder internal toothed hollow gear = hollow roller 7. 17 Cooling channel in 7 _TE expansion temperature

Claims (26)

A process for producing a syntactic foam type polymer composition, preferably a pressure sensitive adhesive composition, comprising:
a) at least a majority of the closed-cell voids are obtained by introducing expandable microspheres into the matrix material and subsequent mixing;
b) Expansion of the expandable microspheres is performed after they are introduced into the matrix material,
c) the temperature distribution in the mixer (1) is non-uniform in a plane perpendicular to the transport direction of the mixer (1),
d) The first surface (3) which becomes the boundary of the mixing space (2) of the mixer (1) is in contact with the first boundary surface (3) by the polymer composition containing the microspheres. As long as it should be kept at a sufficiently high temperature in a plane perpendicular to the transport direction of the mixer (1) so as to reach a temperature (T _E ) sufficient to start and continue its expansion,
e) On the other hand, in the same plane perpendicular to the transport direction of the mixer (1), the second surface (4) which becomes the boundary of the mixing space (2) of the mixer (1) contains microspheres. As long as the polymer composition is in contact with this second boundary surface (4), it is kept at a sufficiently low temperature so that it does not reach a temperature (T _e ) sufficient to start and continue its expansion,
A method as described above, characterized in that f) This mixer (1) is a planetary gear extruder,
c ′) And the externally toothed central spindle (5) and its internally toothed hollow gear (7)
d ′) As long as the polymer composition containing the microspheres is in contact with the first of these two elements (5 or 7), it reaches a temperature (Te) sufficient to initiate and continue its expansion. ,
e ′) On the other hand, as long as the polymer composition containing the microspheres is in contact with the second of these two elements (7 or 5), a temperature sufficient to initiate and continue its expansion ( Does not reach T _e ),
The method according to claim 1, wherein: d′ 1) As long as the internally toothed hollow gear (7) of the planetary gear extruder (1) is in contact with the hollow gear (7) the polymer composition containing the microspheres, Kept at a high enough temperature to reach a high enough temperature (T _e ) for continuation,
e′1) On the other hand, the externally toothed sun gear (5) is sufficient to start or continue its expansion as long as the polymer composition containing the microspheres is in contact with this sun gear (5). Kept low enough so that the temperature (T _e ) is not reached,
The method according to claim 2, wherein: d′ 2) The internal toothed hollow gear (7) of the planetary gear extruder (1) has its start of expansion as long as the polymer composition containing the microspheres is in contact with the hollow gear (7) or Kept at a low enough temperature so that it does not reach a temperature sufficient to continue (T _e ),
e′2) On the other hand, the externally toothed sun gear (5) is sufficient to initiate and continue its expansion as long as the polymer composition containing the microspheres is in contact with this sun gear (5). Kept high enough to reach the temperature (T _e ),
The method according to claim 2, wherein:   The temperature difference between the first surface (3) that is the boundary of the mixing space (2) of the mixer and the second surface (4) that is the boundary of the mixing space (2) of the mixer is at least 50 ° C. The process according to claim 1, characterized in that it is preferably in the range of 65C to 90C.   6. The temperature difference between the hot hollow gear and the cold sun gear is at least 50 [deg.] C., preferably in the range of 65 [deg.] C. to 90 [deg.] C. The method as described in one.   Process according to claim 6, characterized in that acrylates and / or methacrylates are used as matrix base polymer, optionally together with a tack-increasing resin.   6. The temperature difference between the low temperature hollow gear and the high temperature sun gear is at least 50 [deg.] C., preferably in the range of 65 [deg.] C. to 90 [deg.] C. The method as described in one.   Polyethylene and / or polypropylene and / or polyethylene-vinyl acetate and / or polypropylene-vinyl acetate and / or a copolymer of some or all of the above monomers, as matrix base polymer, optionally together with a tackifier resin, 9. Method according to claim 8, characterized in that it is used.   The central spindle (5) does not have a planetary roller (6) rotating through it in its uptake region, so that the planetary roller (6) starts only further downstream as viewed in the transport direction. Planetary gear extruder (1) as a device for carrying out the method according to claim 2, characterized in that   Method according to claim 7, characterized in that the matrix-based polymer is introduced into the cold central spindle 5 in the intake area of the planetary gear extruder (1).   10. Method according to claim 9, characterized in that the matrix base polymer is introduced into the hot central spindle 5 in the intake area of the planetary gear extruder (1).   The expandable microspheres are first suspended in water before being introduced into the polymer composition, and after leaving in the aqueous environment for at least 12 hours, the water-microsphere suspension is The process according to claim 1, characterized in that it is introduced into the forming polymer composition and mixed.   14. The method of claim 13, wherein the carbon black is mixed into the polymer composition, wherein the carbon black is first emulsified or suspended in water, and then the microspheres are added to the carbon black-water emulsion. Alternatively, after being suspended in the suspension, the carbon black-water-microsphere suspension is introduced into the matrix-forming polymer composition and mixed.   15. A method according to claim 13 or 14, characterized in that the expansion of the microsphere is initiated at a temperature below the expansion start temperature of the microsphere used as directed by the manufacturer of the microsphere.   16. A method according to claim 15, characterized in that the expansion of the microspheres is initiated at least 8 [deg.] C below their expansion start temperature, preferably 10 [deg.] C to 25 [deg.] C.   Characterized in that the water content of the mixture is further reduced at any time after the aqueous microsphere suspension is introduced into the matrix material, preferably near the end of mixing or shortly before molding. The method according to claim 13, 14, 15 or 16.   18. A method according to claim 17, characterized in that the water evaporates by applying sub-atmospheric pressure only after a uniform distribution of microspheres in the matrix-forming composition is achieved. A polymer composition containing microspheres is
f) applied in a single layer to the support of the single-sided self-adhesive tape to be formed, or g) applied in a single layer to each of the two sides of the support of the double-sided self-adhesive tape to be formed Or h) applied in a single layer to the liner, after which the composite is layered with the composite after the first mirror coating, or itself is a double-sided self-adhesive without a support The method according to claim 1, wherein the method is any one of forming a tape.   4. A method according to claim 3, characterized in that the coolant flows inside the sun roller (5) opposite the polymer transport direction.   5. A method according to claim 4, characterized in that the coolant flows in the hollow roller (7) opposite the polymer transport direction.   The apparatus for carrying out the method according to claim 18, characterized in that it has a sub-atmospheric pressure zone downstream of the planetary gear extruder and upstream of the first or only molding device.   An extrudate foamed with expandable microspheres, characterized in that the average height of the peaks and valleys is less than 12 μm, preferably less than 5 μm.   A self-adhesive tape comprising or consisting of a foamed adhesive composition produced by the method of claim 1.   25. Self-adhesive tape according to claim 24, characterized in that the adhesive layer of the single-sided self-adhesive tape or both adhesive layers of the double-sided self-adhesive tape are manufactured in a single layer.   26. Self-adhesive tape according to claim 24 or 25, characterized in that at least one self-adhesive surface has an average height of peaks and valleys of less than 12 [mu] m, preferably less than 5 [mu] m.

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