Silicone-containing pressure-sensitive adhesive and pressure-sensitive adhesive products such as an adhesive tape or a label, and process for producing same

Abstract

An adhesive containing silicone, in the form of an adhesive compound which contains at least a first adhesive component and a second adhesive component containing silicone is provided. The second, silicon-laced adhesive component consists of a non-crosslinked polysiloxane. The kinematic viscosity of the non-crosslinked polysiloxane is at least 100,000 mm.sup.2/s and at most 10,000,000 mm.sup.2/s or that the molar mass of the non-crosslinked polysiloxane is less than 10,000 g/mol, and the second, silicone-containing adhesive component is microencapsulated. Alternatively it can be provided that the molar mass of the polysiloxane is at least 80,000 g/mol and at most 500,000 g/mol, or that the kinematic viscosity of the non-crosslinked polysiloxane is less than 100,000 mm.sup.2/s, and the second, silicone-containing adhesive component is microencapsulated.

Claims

1. An adhesive comprising a first adhesive component and a second, silicone-containing adhesive component, wherein the second, silicone-containing adhesive component consists of a non-crosslinked polysiloxane that is or without microencapsulation, wherein the second, silicone-containing adhesive component has a molar mass of at least 100,000 g/mol and at most 500,000 g/mol; whereby the molar mass is calculated using the formula:
M.sub.n=[(log v-1)/0.01231].sup.2, wherein v is the numerical value of a kinematic viscosity in mm.sup.2/s at 25 C. from measurements of the viscosity in accordance with DIN 53019-1:2008-09, and M.sub.n is the numerical average of the molar mass, whereby the bond strength of the adhesive on steel lies in a range between 5 N/cm and 10 N/cm measured according to DIN EN 1939:2003-12.

2. The adhesive according to claim 1, wherein the second, silicone-containing adhesive component is present in the adhesive in a ratio of 1.0 to 10.0 percent by mass.

3. The adhesive according to claim 1, wherein the surface tension of the non-crosslinked polysiloxane at 25 C. is in a range between 18.0 mN/m and 21.7 mN/m, measured according to DIN 53 914:1997-07.

4. The adhesive according to claim 1, wherein the first adhesive component is a pressure-sensitive adhesive, the pressure-sensitive adhesive is at least one of the following: based on a synthetic or natural rubber, a dispersion adhesive based on a polyacrylic acid ester, a hot-melt adhesive based on a UV-crosslinking polyacrylic acid ester, or a UV-polymerizing polyacrylic acid ester.

5. A pressure-sensitive adhesive product comprising a band-shaped carrier upon which at least on one side a pressure-sensitive adhesive in the form of an adhesive composition is applied, wherein the adhesive composition exhibits the features of claim 1.

6. A pressure-sensitive adhesive product, comprising a carrier material upon which at least on one side a pressure-sensitive adhesive in the form of an adhesive composition is applied, wherein the adhesive composition exhibits the features of claim 1.

7. The pressure-sensitive adhesive product according to claim 6, wherein the carrier material consists of a paper, a film, or a textile material.

8. The pressure-sensitive adhesive product according to claim 7, wherein the film or textile material consists of a polyolefin, a polyester, a polyamide, a polystyrene, or another synthetic material.

9. The pressure-sensitive adhesive product according to claim 5, wherein the carrier exhibits a thickness in a range from 10 m to 500 m.

10. The pressure-sensitive adhesive product according to claim 5, wherein the bond strength on steel is in a range between 5 N/cm and 10 N/cm, measured according to DIN EN 1939:2003-12.

11. The pressure-sensitive adhesive product according to claim 10, wherein the bond strength to steel, measured according to DIN EN 1939:2003-12, can be reduced by a maximum of 10 percent compared to a similar pressure-sensitive adhesive product which does not contain the second, silicone-containing adhesive component.

12. The pressure-sensitive adhesive product according to claim 5, wherein the adhesive composition is covered with an additional liner, the additional liner consisting of a paper or foil which is siliconized on one or both sides.

13. A process for manufacturing a pressure sensitive adhesive product comprising a band-shaped carrier upon which at least on one side a pressure-sensitive adhesive in the form of an adhesive composition is applied, the process comprising: providing a base product having a width in a range from 100 mm to 2500 mm, and cutting or stamping the base product with a cutting tool, wherein the cutting tool comes into direct contact on cutting edges with the pressure-sensitive adhesive, wherein the adhesive composition comprises a first adhesive component and a second, silicone-containing adhesive component, the second, silicone-containing adhesive component consisting of a non-crosslinked polysiloxane, without microencapsulation; wherein the second, silicone-containing adhesive component has a molar mass of at least 100,000 g/mol and at most 500,000 g/mol; whereby the molar mass is calculated using the formula:
M.sub.n=[(log v-1)/0.01231].sup.2, wherein v is the numerical value of a kinematic viscosity in mm.sup.2/s at 25 C. from measurements of the viscosity in accordance with DIN 53019-1:2008-09, and M.sub.n is the numerical average of the molar mass, whereby the bond strength of the adhesive on steel lies in a range between 5 N/cm and 10 N/cm measured according to DIN EN 1939:2003-12.

14. The process according to claim 13, wherein the pressure-sensitive adhesive product is an adhesive tape which is parted off from a roll with up to a thousand layers on top of one another via circular blades or styli, or that the pressure-sensitive adhesive product is a label which is cut or stamped from a stack of up to a thousand sheets on top of one another via a guillotine shear.

Description

DETAILED DESCRIPTION OF THE INVENTION

(1) In the design forms of the invention listed below, various pressure-sensitive adhesive formulations which are preferred in accordance with the invention are presented, which specifically differ in the nature of the first component of the pressure-sensitive adhesive composition. These formulations are each compared with alternate formulations which contain no polydimethylsiloxane.

(2) Table 1 details examples of formulations with a synthetic rubber adhesive.

(3) The silicone oil named in this tableAK 500,000 from Wackeris a polydimethylsiloxane with a kinematic viscosity of 500,000 mm.sup.2/s.

(4) TABLE-US-00001 TABLE 1 Formulation examples 1a (comparison example) and 1b (according to invention) Manufacturer 1a 1b Synthetic rubber Vecor 4114 Dexco 32% 30% Terpene phenolic Dertophene T DRT 18% 17% resin Rosin Granolite P DRT 18% 17% Soft resin Wingtack 10 Cray Valley 26.5% 25% PE Wax A-C8 Honeywell 5% 5% Anti-oxidant Irganox 1010 BASF 0.5% 0.5% Silicone oil AK 500,000 Wacker 5%

(5) In general the kinematic viscosity of the polydimethylsiloxane used in accordance with the invention should be at least 50,000 mm.sup.2/s, preferably at least 100,000 mm.sup.2/s. A value of 10 million mm.sup.2/s can be considered an upper limit.

(6) The soft resin listed in the table is a tackifying synthetic C5 resin with a softening point of less than 20 C.

(7) Anti-oxidant in table 1 refers to the admixture of substances which counteract the thermo-oxidative degradation of a polymer, here a hot-melt adhesive. Sterically hindered phenols, in this case specifically the aforementioned Irganox 1010, are preferred as radical scavengers.

(8) Both example substances were applied as hot-melt adhesives to 80 g/m.sup.2 paper and covered with a layer of 100 g/m.sup.2 paper which was coated in silicone on one side.

(9) Table 2 details examples with an acrylate dispersion adhesive, with consideration of the various solid states, i.e. without water content.

(10) An acrylate dispersion, as it is listed in table 2, is understood to mean an aqueous dispersion of a polyacrylic acid ester produced by emulsion polymerization.

(11) TABLE-US-00002 TABLE 2 Formulation examples 2a (comparison example) and 2b (according to invention) Manufacturer 2a 2b Acrylate Acronal V215 (solid BASF 46% 43.5% dispersion content 69%) Acrylate Acronal 80D (solid BASF 20% 19% dispersion content 50%) Resin Dermulsene RE802 DRT 33.5% 32% dispersion (solid content 52%) DOSS* OT75 Airproducts 0.5% 0.5% Silicone oil HV 495 (solid content Dow Corning 5% dispersion 40%) *Dioctyl sulfosuccinate

(12) The silicone oil dispersion listed in table 2 is an aqueous dispersion of a polydimethylsiloxane. This is not produced by emulsion polymerization, but rather by a subsequent emulsification of a polydimethylsiloxane. Solid content in the second column refers to the respective solid content in the dispersion. Silicone oil dispersion is a milky white fluid which can exhibit a kinematic viscosity in a range between 78,000 mm.sup.2/s and 200,000 mm.sup.2/s, whereby the molar mass of the silicone oil reaches at least 100,000 g/mol.

(13) Both example substances were applied at a grammage of 18 g/m.sup.2 to a paper with a specific basis weight of 90 g/m.sup.2 siliconized on one side, where it was dried and then transferred to a paper with a specific basis weight of 80/m.sup.2.

(14) Table 3 details examples of formulations with a UV acrylate adhesive.

(15) TABLE-US-00003 TABLE 3 Formulation examples 3a (comparison example) and 3b (according to invention) Manufacturer 3a 3b Polyacrylate AcResin 3502 BASF 100% 97% Silicone oil AK 500,000 Wacker 3% Chemistry

(16) The silicone oil named in this tableAK 500,000 from Wackeris a polydimethylsiloxane with a kinematic viscosity of 500,000 mm.sup.2/s.

(17) Both example substances were applied at a grammage of 30 g/m.sup.2 to a PET film with a thickness of 50 m which was siliconized on one side, where they were crosslinked via a UV-C dose of 65 mJ/cm.sup.2 and then transferred to a non-siliconized 50 m-thick PET foil. The UV-C dose was measured with the Power Puck dosimeter from EIT Company of Sterling, Va.

(18) The samples were used to determine the typical pressure-sensitive adhesive base data representative of adhesion and cohesion, in the form of bond strength and shear strength.

(19) Additionally, the cuttability of the self-adhesive material was determined in a laboratory test. To this end, two DIN-A4 sheets of the adhesive material were placed atop one another and 5 mm wide strips were cut with commercially available guillotine shears with smooth, clean steel blades. The blade had a width in a range of 50 to 60 mm. The contamination of the blade was checked after multiple cuts.

(20) The examples demonstrated the properties listed in table 4.

(21) TABLE-US-00004 TABLE 4 Comparison of properties of the examples Example Example Example Example Example Example 1a 1b 2a 2b 3a 3b Bond >8* >8* 7 7 6.5 6 strength (on steel) [N/cm] DIN EN 1939 Shear >10000 >10000 >10000 >10000 >10000 >10000 strength 625 mm.sup.2; 23 C. [min] Cutting test Blade Blade Blade Blade Blade Blade with 5 cuts very sticky to very sticky to very sticky to sticky to 1 mm, sticky to 1 mm, sticky to 1 mm, 45 mm, strips do 45 mm, strips do 45 mm, strips do strips not cling strips not cling strips not cling cling to to blade cling to to blade cling to to blade blade blade blade Cutting test Blade Blade Blade with 50 cuts sticky to sticky to sticky to 3 mm, 2 mm, 3 mm, strips do strips do strips do not cling not cling not cling to blade to blade to blade *Paper tear

(22) DIN EN 1939 Adhesive Tapes: Determining Bond Strength as mentioned in table 4 is the version DIN EN 1939:2003-12. The bond strength on steel can lie specifically between 5 N/cm and 10 N/cm, preferably in a range between 6 N/cm and 8 N/cm, measured according to DIN EN 1939:2003-12.

(23) In general according to the invention it can be reached that the bond strength to steel is reduced only by 10 percent maximum, measured according to DIN EN 1939:2003-12 and compared to a pressure-sensitive adhesive product which does not contain the second, silicone-containing adhesive component, but for which the remaining components of the adhesive composition are in the same ratio to one another.

(24) Shear strength was determined according to DIN EN 1943:2003-01 Adhesive TapesMeasuring Shear Resistance under Static Load; German edition EN 1943:2002.

(25) The results clearly demonstrate that the invention results in greater workability during cutting processes while excluding negative effects on bond strength and shear strength.

(26) The following additional practical tests were carried out with the samples:

(27) A stack with dimensions 70 cm100 cm with 200 sheets of adhesive material were cut into small squares with dimensions of 5 cm5 cm using a guillotine shear with smooth blades. With the materials from the examples according to the invention 1 b, 2b, and 3b, this was possible with no problems, but with the materials from the comparison examples 1a, 2a, and 3a, the sheets adhered after the third cut and clung to the blade, so that cleanly cutting and depositing the square stack was no longer possible.

(28) The invention is not limited to the design examples illustrated here, but rather includes in the scope of its claims all equivalent designs and applications in the context of the invention. Thus it is conceivable that, in contrast to the polydimethylsiloxane described in the example, a polysiloxane is used in which other substituents in addition to and/or instead of methyl groups, such as acryl radicals with more than one carbon atom, phenyl radicals and/or halogens, are bonded to the main chain.

(29) Concerning the aforementioned influence of the molar mass of the polydimethylsiloxane, its migration capacity decreases with an increasing degree of polymerization n, and increases with a decreasing degree of polymerization n. If, for instance, in example 1b an AK 50 with less than 100 dimethylsiloxane units in the polymer chain is used instead of AK 500,000, which consists of significantly more than 1000 dimethylsiloxane units in the polymer chain, the disadvantage is observed that after warm storage of only 24 hours at 70 C., there is visible silicone migration into the paper carrier.

(30) However, the use of low molecular weight silicone oils appears to be advantageous if they are microencapsulated, especially with a molar mass of the polysiloxane of less than 10,000 g/mol, as provided according to the invention. Generally, due to the still sufficient fluidity, microencapsulation can alternately be provided according to the invention in all cases in which the kinematic viscosity of the non-crosslinked polysiloxane is less than 100,000 mm.sup.2/s.

(31) Microencapsulation is generally understood to mean the coating of very fine drops of a mostly fluid active substance with a thin-walled inert material. Concerning the invention, such encapsulation prevents unwanted migration of low molecular weight silicone oil. At the moment of cutting, the shell of the microcapsules is damaged by the cutting tool. The silicone oil which constitutes the fluid core is thereby released and locally in a very restricted area performs its function as a release agent. The particle size of the microcapsules can lie in a range between 3 m and 800 m, preferably in a range between 5 m and 100 m. Materials considered inert are those which do not chemically react to most substances under ideal conditions, such as pressure and temperature. For example, ceramic, fluoroplastics such as PTFE, and the precious metals gold and platinum are considered inert, as well as gelatin-encapsulated medications.

(32) Microencapsulation of silicone oil is known in and of itself, and described for example in patent DE 101 56 672 A1. The example productions of particles described therein are microcapsules with an average particle size of 3 m and 5 m, which have a liquid phase of silicone oil enclosed within capsule walls made of polyurea-containing material.

(33) Although there is no indication in DE 101 56 672 A1 of using microcapsules in general and microencapsulated silicone oil specifically in adhesives, specifically pressure-sensitive adhesives, and preferably adhesive articles made with pressure-sensitive adhesives, it has been found that the material of the capsule walls as described is compatible with the pressure-sensitive adhesives preferred as materials for the first adhesive component used in the context of the invention, on the basis of rubber, of dispersion adhesives on the basis of polyacrylic acid esters, of hot-melt adhesives on the basis of UV crosslinked polyacrylic acid esters, or of UV polymerized polyacrylic acid esters, and that the adhesive properties are not negatively affected, at least when the second, silicone-containing adhesive component is present in a proportion of 1.0 to 10.0 percent by mass.

(34) Microencapsulation is only sensible, however, when it is ensured that the microcapsules will be broken open during useduring cutting in the context of the inventionand thereby the silicone is released as an active agent. For example, in a simple bonding of adhesive tape, as is provided for in WO 99/26572 A1, which contained a microencapsulated substance in its adhesive layer, the necessary opening of the capsules and thus the desired effect attributed to the encapsulated substance could not be achieved.

(35) While the above description constitutes the preferred embodiment of the present invention, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope and fair meaning of the accompanying claims.