Method for Homogenously Incorporating Filler into a Self-Adhesive Compound, in Particular a Thermally Crosslinkable Self-Adhesive Compound, Based on Non-Thermoplastic Elastomer

Abstract

The invention relates to a method for homogenously incorporating filler into a self-adhesive compound, in particular a thermally crosslinkable self-adhesive compound, based on non-thermoplastic elastomer in a continuously working unit with a filling part and a compounding part. The self-adhesive compound contains at least one solid component, at least one liquid component, and at least one filler, and the method has the following steps: (a) feeding at least part of the at least one solid component, such as the non-thermoplastic elastomer in particular, and optionally part of the at least one liquid component to the filling part; (b) transferring the components of step (a) from the filling part to the compounding part; (c) optionally adding additional solid components or additional parts of the solid components to the compounding part; (d) adding the at least one liquid component to the compounding part if the liquid component was not already added to the filling part in step (a); (e) producing a homogenous self-adhesive compound in the compounding part; and (f) discharging the self-adhesive compound. The invention is characterized in that at least part of the at least one filler is pre-dispersed into at least one dispersion liquid in a separate unit and the dispersion obtained in this manner is added to the compounding part. The method prevents high sheering or frictional energies while introducing the filler into the compounding part of the continuously working unit and thus allows the use of temperature-sensitive components, such as temperature-sensitive chemical crosslinking agents in particular.

Claims

1. A process of homogeneously imcorporating filler into thermally crosslinkable self-adhesive composition based on a non-thermoplastic elastomer in a continuously operating assembly with a feed section and with a compounding section, where the self-adhesive composition comprises at least one solid component, at least one liquid component and at least one filler, and where the process comprises the following steps: (a) charging of at least one portion of the at least one solid component, and optionally of a portion of the at least one liquid component, into the feed section; (b) transfer of the components from step (a) from the feed section into the compounding section; (c) optional addition of further solid components or of further portions of the solid components into the compounding section; (d) addition of the at least one liquid component into the compounding section, insofar as not yet charged in step (a) into the feed section; (e) production of a homogeneous self-adhesive composition in the compounding section; and (f) discharge of the self-adhesive composition wherein, at least a portion of the at least one filler is added after predispersion in at least one dispersion liquid in a separate assembly, the resultant dispersion being added into the compounding section.

2. The process of claim 1, wherein the dispersion liquid is at least one plasticizer such as (mineral) oil or fat, plasticizing resin and/or tackifier resin.

3. The process of claim 1, wherein at least one of the solid components is non-thermoplastic elastomer, thermoplastic elastomer, tackifier resin, thermal crosslinking agent and/or aging inhibitor.

4. The process of claim 1, wherein at least one of the liquid components is non-thermoplastic elastomer, thermoplastic elastomer, plasticizer such as fat or oil, dye, plasticizing resin, tackifier resin and/or thermal crosslinking agent.

5. The process of claim 1, wherein the non-thermoplastic elastomer is selected from the group of the natural rubbers, the randomly copolymerized styrene-butadiene rubbers (SBR), the butadiene rubbers (BR), the acrylonitrile-butadiene rubbers (NBR), the synthetic polyisoprenes (IR), the butyl rubbers (IIR), the halogenated butyl rubbers (XIIR), the acrylate rubbers (ACM), the ethylene-vinyl acetate copolymers (EVA), the polyolefins, the polyurethanes and blends thereof.

6. The process of claim 1, wherein 10 to 50% by weight, based on the total elastomer content of the self-adhesive composition, of thermoplastic elastomer is charged or, respectively, added alongside the non-thermoplastic elastomer.

7. The process according to claim 1, wherein in the compounding section at least one thermal crosslinking agent selected from sulfur crosslinking systems, accelerated sulfur crosslinking systems, reactive phenolic resin crosslinking systems and diisocyanate crosslinking systems is added.

8. The process of claim 1, wherein the filler is selected from oxides of alkali metals, oxides of alkaline earth metals or oxides of transition metals, mixtures of these oxides and lignin.

9. The process of claim 1, wherein the self-adhesive composition is produced without solvent.

10. The process of claim 1, wherein the continuously operating assembly is a multiscrew extruder, and where the compounding section of the multiscrew extruder includes at least two coupled planetary barrel sections.

11. The process of claim 10, wherein the planetary barrel section of the planetary-gear extruder comprises at least half of the possible number of planetary spindles.

12. The process if claim 1, wherein the separate assembly is a multiscrew extruder having at least one barrel section, and into which assembly components can be added continuously during the process.

13. The process of claim ,1 wherein the entire quantity of the at least one filler is predispersed in the at least one dispersion liquid.

14. The process of claim 1, wherein the temperature of the self-adhesive composition on discharge from the continuously operating assembly is not in excess of 125° C.

15. The process of claim 1, wherein the self-adhesive composition is coated onto a material which takes the form of a web.

16. The process of claim 15, wherein the coating of the material which takes the form of a web is achieved with a roll unit or calender unit, where the self-adhesive composition is molded to the desired thickness during passage through one or more nips prior to transfer onto the material which takes the form of a web.

17. The process of claim 15, wherein in a proess step downstream of the coating procedure, the self-adhesive composition is crosslinked.

18. A self-adhesive composition formed by the process of claim 1.

19. The process of claim 17, wherein the self-adhesive composition is thermally crosslinked.

20. The process of claim 2, wherein the dispersion liquid is at least one tackifier resin.

Description

EXAMPLES

[0103] The compounding assembly used in the examples of the process of the invention (and also in the comparative example) was a planetary-gear extruder from ENTEX Rust & Mitschke GmbH. It consisted of a single-screw feed section (1) and four coupled planetary barrel sections (2a-2d) with length respectively 400 mm and with diameter in each case 70 mm. Between the planetary barrel sections there were restrictor rings (3a-3c) with differently dimensioned flow cross sections through which the compositions are passed during transition from the previous planetary barrel section into the respective following downstream barrel section. The restrictor rings (3a-3c) retain the planetary spindles of the extruder in fixed location and subject the composition to a certain shear effect.

[0104] The free flow cross section was 330 mm.sup.2 in the case of the first restrictor ring (3a) between the first (2a) and the second planetary barrel section (2b), 185 mm.sup.2 in the case of the second restrictor ring (3b) between the second (2a) and third planetary barrel section (2c), and 855 mm.sup.2 in the case of the third restrictor ring (3c) between the third (2c) and fourth planetary barrel section (2d). The first two planetary barrel sections (2a, 2b) behind the feed section (1) were provided with respectively seven planetary spindles; the last two planetary barrel sections downstream (2c,2d) respectively comprised six planetary spindles. The central spindle and the planetary barrel sections (2a-2d) respectively had their own temperature-controlled circuit. Water was used as temperature-control medium.

[0105] A twin-screw extruder (6) from LEISTRITZ with screw diameter 50 mm was used as separate assembly (auxiliary assembly) for dispersion of the fillers in examples of the process of the invention. The active screw length was 40*D (D=diameter of extruder screw). The solid resin to be melted was added by way of a commercially available gravimetric metering device into the aperture of the first barrel section; the fillers were metered into the system downstream, into an aperture of the fifth barrel section by way of commercially available gravimetric metering devices. Side-feed equipment was used in these examples to introduce the fillers into the twin-screw extruder.

[0106] The screw length for melting of the resin and for dispersion of the fillers into the resin melt was respectively 8*D. In these regions, the twin screws consisted of a combination of kneading-block units with 45°, 60° and 90° offset. The remainder of the screw consisted exclusively of closely intermeshing conveying elements.

[0107] The planetary-gear extruder was in each case coupled to an extrex EX 45-5 electrically heated melt pump from MAAG, which served as unit for discharge of the self-adhesive composition from the planetary-gear extruder. The self-adhesive composition produced in the planetary-gear extruder was transferred by way of this melt pump and a heatable hose to a low-shear twin-screw extruder (not shown in the figures) in which it was freed from air under the influence of vacuum. The devolatilizing twin-screw extruder was a ZE42×36D from Krauss Maffei Berstorff. It was operated with a barrel temperature of 110° C. The vacuum-dome pressure used for the devolatilization of the self-adhesive composition was below 10 mbar absolute.

[0108] FIG. 1 shows the structure of the planetary-gear extruder used and the location of addition of the components into the planetary-gear extruder in the comparative example. FIGS. 2 to 5 show the structure of the planetary-gear extruder used and of the twin-screw extruder (auxiliary assembly) for predispersion of filler, and also the respective locations of addition of the components into the planetary-gear extruder or twin-screw extruder in inventive examples 1 to 4. Details can be obtained from the description relating to the respective example (or comparative example).

Raw Materials Used

[0109] The raw materials listed in table 1 were used in inventive examples 1 to 4 and, respectively, the comparative example.

TABLE-US-00001 TABLE 1 Raw material used. Name Type Producer Elastomer NR V 145 Natural rubber Weber&Schaer Nipol Acrylonitrile-butadiene Zeon rubber Vistanex Butylene/isobutylene rubber Exxon Elast SIS Quintac (polystyrene- Zeon polyisoprene block copolymer) Adhesive resin Regalite R1100 Hydrocarbon resin Eastman Chemical DT 110 Terpene phenol resin DRT Dercolyte S 115 β-pinene resin DRT Dertophene T Terpene phenol resin DRT Resin 100 Colophonium resin (acid) Diamantino Malho Crosslinking- PA 510 Alkylphenol resin SI-Group agent resin Plastifying agent Lanolin Lanolin Lanolines Stella Yellow oil (Ondina Hydrocarbon with complex Shell 919) variable composition Filler ZnO white Zinc oxide Lanxess Durafill 200 Silicon dioxide Grace MS 40 chalk filler Calcium carbonate Vereinigte Kreidewerke Dammann Aging inhibitor Irganox 1076 Sterically hindered phenol BASF SE Irganox 1726 2,4-bis(dodecylthiomethyl)- BASF SE 6-methylphenol MMBI 2-Mercapto-4(5)-methyl- Lanxess benzimidazole Sontal 2,5-di-tert- Addivant (LOWINOX ® pentylhydroquinone AH25)

COMPARATIVE EXAMPLE

[0110] Formulation A stated in table 2 was used in the comparative example.

TABLE-US-00002 TABLE 2 Formulation A. Component Composition TH 21 NR V 145 46.5% ZnO white 9.3% DT110 resin 14.0% S115 resin 20.0% Nipol 4.7% PA 510 resin 4.7% Sontal 0.8%

[0111] The natural rubber NR V 145, the filler zinc oxide (ZnO white) and the Sontal were metered into the single-screw feed section (1) of the planetary-gear extruder. The resins were metered in the solid state by way of side-feed equipment (4a-4c) into the respective apertures of the planetary barrel sections (2a-2c) of the planetary-gear extruder. The tackifier resin DT110 here was added in the first planetary barrel section (2a), the tackifier resin S115 was added in the second planetary barrel section (2b), and the crosslinking-agent resin PA 510 was added in the third planetary barrel section (2c).

[0112] The Nipol was preheated at 70° C. in a melting-tank unit (not shown) and metered continuously into the planetary-gear extruder by way of the melt pump integrated in the base of the melting tank into a bore of the restrictor ring (3b) located behind the second planetary barrel section (2b) and in front of the third planetary barrel section (2c).

[0113] FIG. 1 shows the division of the formulation constituents for the mode of operation selected here.

[0114] The total throughput of all components was 50 kg/h. The temperature of the cooling water in the entry to the central spindle was 8° C.; the entry temperature of the water for temperature-control of the planetary barrel sections (2a-2d) was 90° C.

[0115] The rotation rate of the central spindle was varied in a range between 70 revolutions per minute and 130 revolutions per minute. At no spindle rotation rate was it possible to obtain a homogeneous self-adhesive composition; instead, there were always undispersed agglomerates of zinc oxide discernible by the naked eye in the polymer matrix. At the highest rotation rate tested here, the temperature of the self-adhesive composition at discharge was 131° C.

Inventive Example 1

[0116] The formulation A was likewise used in the process of the invention for production of a high-temperature cloth tape based on cotton backing, but the zinc oxide (ZnO) was now first predispersed in a resin melt before it was added to the planetary-gear extruder.

[0117] The natural rubber NR V 145 and the Sontal were metered by means of gravimetric metering devices into the single-screw feed section (1) of the planetary-gear extruder. The tackifier resin DT110 was added by way of a side-feed extruder (4a) which had been coupled to the planetary-gear extruder at the upstream end of the first planetary barrel section (2a).

[0118] In the separate twin-screw extruder (6), the tackifier resin S115 was melted; ZnO white was mixed therewith downstream, and a homogeneous dispersion of zinc oxide in the resin melt was then produced. The twin-screw extruder (6) was operated with a screw rotation rate of 80 revolutions per minute and a barrel temperature of 170° C. The dispersion was then fed continuously into the planetary-gear extruder by way of an aperture (5) in the barrel-section wall at the ingoing end of the second planetary barrel section (2b).

[0119] As in the comparative example, the Nipol was preheated at 70° C. in a melting-tank unit and metered continuously into the planetary-gear extruder by way of the melt pump integrated in the base of the melting tank into a bore of the restrictor ring (3b) located behind the second planetary barrel section (2b) and in front of the third planetary barrel section (2c).

[0120] The crosslinking agent resin PA 510 was added by way of a further side-feed extruder (4c), which had been coupled on the third planetary barrel section (2c) of the planetary-gear extruder.

[0121] FIG. 2 shows the division of the formulation constituents for the mode of operation selected here.

[0122] The total throughput of all components was 50 kg/h. The planetary-gear extruder was operated with a rotation rate of the central spindle of 90 revolutions per minute. The cooling-water temperature in the entry to the central spindle was 8° C.; the entry temperature of the water for temperature-control of the planetary barrel sections (2a-2d) was 90° C.

[0123] The process of the invention gave a homogeneous polymer matrix in which no agglomerated particles of any kind were discernible optically, in particular by the naked eye. The discharge temperature of the self-adhesive composition obtained at the end of the planetary-gear extruder was 111° C.

[0124] The self-adhesive composition was then transferred by means of melt pump and heated hose to a turn-screw extruder in which it was freed from the included air by the effect of a 3 mbar vacuum.

[0125] Immediately after the production process, the self-adhesive composition, freed from air, was applied to a cotton backing with weight per unit area 200 g/m.sup.2 and with layer thickness 120 μm which had been impregnated by processes conventionally used in the sector and which had a known release layer.

[0126] The method for coating of the adhesive composition was analogous to that in example 4, with an operating width of 300 mm. All rolls were temperature-controlled to 140° C. Coating speed was 50 m/min.

[0127] The adhesive bond strength of the resultant adhesive tape was 4.5-5.5 N/cm on steel and 2.0-2.5 N/cm on PE, and said tape was suitable as masking tape that withstands short periods of exposure to temperatures up to 140° C. The crosslinking delta of the adhesive composition at 180° C. crosslinking temperature was 10 000 Pa*s.

Inventive Example 2

[0128] The following formulation B (table 3) was used for production of general-purpose adhesive tapes with woven-fabric backings.

TABLE-US-00003 TABLE 3 Formulation B. Component Composition La NRE146 NR V 145 19.2% Vistanex 9.0% Dertophene T 15.0% Resin 100 15.1% Lanolin 16.0% Yellow oil 3.8% ZnO white 20.5% Irganox 1076 1.0% MMBI 0.5%

[0129] The experimental setup used for production of this self-adhesive composition was analogous to that of example 1.

[0130] The elastomers NK V 145 and Vistanex, and also the aging inhibitors Irganox 1076 and MMBI, were metered continuously by way of gravimetric metering devices into the single-screw feed section (1) of the planetary-gear extruder. One third of the quantity of Resin 100, corresponding to 5% by weight, based on the entire formulation, was metered in the form of solid resin by way of a side-feed extruder (4a) into the first planetary barrel section (2a).

[0131] With extruder parameters the same as those in example 1, the zinc oxide white was dispersed in the Dertophene T resin and a partial quantity of the Resin 100 in the twin-screw extruder (6). To this end, the Dertophene T resin, and also two thirds of the resin quantity of Resin 100, corresponding to a proportion of 10.1% by weight, based on the entire formulation, were melted, and the entire quantity of zinc oxide was admixed therewith. The zinc oxide, finely dispersed in the resin melt, was then fed continuously into the planetary-gear extruder by way of an aperture (5) in the barrel-section wall at the ingoing end for the second planetary barrel section (2b).

[0132] The lanolin was liquefied in melting-tank equipment at 70° C. and metered by means of a metering pump into the planetary-gear extruder by way of a radial bore in the second restrictor ring (3b) located before the third planetary barrel section (2c).

[0133] The yellow oil was introduced into the planetary-gear extruder by way of a radial bore in the third restrictor ring (3c) located behind the third barrel roll section (2c).

[0134] FIG. 3 shows the division of the formulation constituents for the mode of operation selected here.

[0135] The total throughput of all components was 50 kg/h. The planetary-gear extruder was operated with a rotation rate of the central spindle of 110 revolutions per minute. The cooling-water temperature in the entry to the central spindle was 8° C.; the entry temperature of the water for temperature-control of the planetary barrel sections (2a-2d) was 90° C.

[0136] The process of the invention gave a homogeneous polymer matrix in which no agglomerated particles of any kind were discernible optically, in particular by the naked eye. The discharge temperature of the self-adhesive composition obtained at the end of the planetary-gear extruder was 99° C.

[0137] The self-adhesive composition was transferred by means of a melt pump coupled to the planetary-gear extruder to a twin-screw extruder in which it was freed from air at a pressure of 3 mbar. This twin-screw extruder was operated with a rotation rate of 100 revolutions per minute. The barrel temperatures were 110° C.

[0138] The resultant adhesive composition was applied in a layer thickness of 115 μm to a woven viscose-cellulose fabric (viscose staple), on the reverse side of which there was a release lacquer conventionally used in the sector, and the weight per unit area of which was 240 g/m.sup.2.

[0139] General-purpose woven-fabric adhesive tapes were produced by the process of inventive example 1. The woven viscose-cellulose fabric, instead of the cotton backing web, was passed here over the lay-on roll, and the adhesive layer of thickness 115 μm shaped by way of the roll-coating calender was then coated onto same. The coating procedure took place at 50 m/min at an operating width of 400 mm.

[0140] The adhesive bond strength of the resultant tape on steel is >4 N/cm, and said tape is suitable as general-purpose adhesive tape for a very wide variety of purposes.

Inventive Example 3

[0141] A double-sided carpet-laying tape based on woven fabric backing was produced with the formulation C (table 4).

TABLE-US-00004 TABLE 4 Formulation C. Component Composition La NRE145 NR V 145 28.2% Dertophene T 15.0% Resin 100 15.1% Lanolin 16.0% Yellow oil 3.8% ZnO white 20.5% Irganox 1076 1.0% MMBI 0.5%

[0142] The experimental setup used for production of this self-adhesive composition was the same as that used in inventive example 2, except that this formulation comprised no Vistanex.

[0143] FIG. 4 shows the division of the formulation constituents for the mode of operation selected here.

[0144] The process of the invention gave a homogeneous polymer matrix in which no agglomerated particles of any kind were discernible optically, in particular by the naked eye. The discharge temperature of the self-adhesive composition obtained at the end of the planetary-gear extruder was 104° C.

[0145] After devolatilization of the self-adhesive composition as described in inventive example 2, the adhesive composition was applied bilaterally with the aid of transfer coating to a commercially available woven viscose-cellulose fabric (viscose staple), the weight per unit area applied being 130 g/m.sup.2 with a layer thickness of 2×100 g/m.sup.2.

[0146] A double-sided carpet-laying tape based on woven fabric backing was produced. A bilaterally siliconized release paper was directly coated with 100 μm by way of the process of inventive example 1. A lamination unit was used to laminate the viscose-staple material onto same, and in a second pass the composite was directly coated with 100 μm of adhesive application onto the open side. The coating speed was 30 m/min.

[0147] The adhesive bond strength of the resultant adhesive tapes on steel was >3.5 N/cm, and said tapes are suitable as double-sided adhesive tapes with tolerance-compensating and damping properties for a very wide variety of purposes.

Inventive Example 4

[0148] An adhesive tape for automotive applications, based on nonwoven polyester backing, was produced with the formulation D (table 5).

TABLE-US-00005 TABLE 5 Formulation D. Component Composition La NRE145 NR V 145 15.3% Elast SIS 15.3% Regalite R1100 33.9% Durafill 200 10.0% MS 40 chalk filler 25.0% Irganox 1726 0.5%

[0149] The two elastomers NR V 145 and Elast SIS were metered separately into the single-screw feed section (1) of the planetary-gear extruder.

[0150] The resin Regalite R1100 was melted continuously in the twin-screw extruder (6) at barrel temperatures of 170° C. The fillers Durafill 200 and MS 40 chalk filler were dispersed homogeneously into this resin melt at an extruder rotation rate of 130 revolutions per minute, and then metered into the planetary-gear extruder by way of an aperture (5) in the housing of the second planetary barrel section (2b).

[0151] The temperature of the second planetary barrel section (2b) was set to 140° C. in order to melt the Elast SIS; the temperature of the three other planetary barrel sections (2a, 2c,2d) was 90° C. Temperature-control of the central spindle was achieved by contact with cooling water, the temperature of which was eight degrees.

[0152] The aging inhibitor Irganox 1726 was heated in a melting-tank unit to 70° C. and introduced into the process in the planetary-gear extruder by way of a radial bore in the second constrictor ring (3b) located between the second planetary barrel section (2b) and the third planetary barrel section (2c).

[0153] FIG. 5 shows the division of the formulation constituents for the mode of operation selected here.

[0154] The total throughput of all formulation components was 40 kg/h. For this formulation 4 the planetary-gear extruder was operated with a rotation rate of the central spindle of 110 revolutions per minute.

[0155] The process of the invention gave a homogeneous polymer matrix in which no agglomerated particles of any kind were discernible optically, in particular by the naked eye. The discharge temperature of the self-adhesive composition obtained at the end of the planetary-gear extruder was 123° C.

[0156] After devolatilization of the composition in a downstream twin-screw extruder as described in inventive example 3, the resultant adhesive composition was applied in a layer thickness of 70 μm to a polyester nonwoven (weight per unit area 70 g/m.sup.2).

[0157] Nonwoven polyester tapes were produced by the process of inventive example 1. The polyester nonwoven, instead of the cotton backing web, was passed here over the lay-on roll, and the adhesive layer of thickness 70 μm shaped by way of the roll-coating calender was then coated onto same. The coating procedure took place at 50 m/min at an operating width of 400 mm.

[0158] The adhesive bond strength of the resultant tape on steel is >3 N/cm, and said tape is suitable as adhesive tape for automotive applications.

Test Methods

Adhesive Bond Strength

[0159] Adhesive bond strength was determined as follows: A steel surface, a polyethylene surface (PE), a glass surface, a PVC surface and sandpaper with grit designation 600 (S600) were used as defined adhesion substrate. The adhesive tape to be tested was cut to size to give a width of 20 mm and a length of about 25 cm, provided with a handling tab, and then immediately pressed five times onto the respectively selected adhesion substrate by a 4 kg steel roller advancing at 10 m/min. A tensile tester (Zwick) was then immediately used to peel the adhesive tape from the adhesion substrate at an angle of 180° and with a peel velocity of 300 mm/min, and the force required for this was measured at room temperature. The measured value (in N/cm) was obtained as average value from three individual measurements.

[0160] For determination of the adhesive bond strength of an adhesive tape on the reverse side of same (ABSRS, adhesive bond strength on reverse side), a test strip was placed, while avoiding any contact with its reverse side, onto the test substrate, for example a steel plate. A second strip is then applied congruently to the reverse side of the first strip with avoidance of air inclusions, and is adhesive-bonded under five double passes of a 4 kg roller.

[0161] The measurement is made by peeling the upper test strip from the lower at a peel angle of 180° at a velocity of 300 mm/min, and determining the force required for this. The results of measurement are stated in N/cm and averaged across three measurements.

[0162] The same test is moreover carried out with the adhesive-bonded samples stored for 3 days at 23° C. and, respectively, 40° C. and thereafter conditioned to room temperature and then subjected to measurement as described above.

Softening Point T.SUB.E

[0163] The data relating to the softening point T.sub.E, also termed softening temperature, of tackifier resins and of various oligomers or polymers relate to the ring-and-ball method in accordance with DIN EN 1427:2007 with appropriate use of the instructions (testing of resin sample instead of bitumen while in other respects retaining the same procedure); the measurements are made in a glycerol bath.