Process for preparing solvent-free polyorganosiloxane pellets and an aqueous dispersion based on a silicone pressure-sensitive adhesive

Abstract

The process for preparing the silicone pressure sensitive adhesive base aqueous dispersion includes the use of solvent-free polyorganosiloxane pellets containing a polyorganosilicate resin and a polyorganosiloxane gum. The silicone pressure sensitive adhesive base aqueous dispersion can be combined with a free radical initiator and dried and cured to form the silicone pressure sensitive adhesive.

Description

Technical Field

[0001] (Cross - reference to related applications) None.

[0002] (Field of the Invention) The present invention relates to a process for preparing a silicone pressure - sensitive adhesive - based aqueous dispersion. More particularly, the present invention relates to a process for preparing a silicone pressure - sensitive adhesive - based aqueous dispersion which, in combination with a free - radical initiator, can be dried and cured to form a silicone pressure - sensitive adhesive. The process for preparing the aqueous dispersion involves the use of solvent - free polyorganosiloxane pellets consisting of a polyorganosilicate resin and a polyorganosiloxane gum.

Background Art

[0003] Introduction Silicone pressure - sensitive adhesives (PSA) have numerous end - uses such as mica tapes and / or masking tapes that have excellent heat resistance, stable adhesiveness, and wetting properties. However, most silicone PSA products in the market are utilized in BTX (benzene, toluene, and xylene) solvents. There is a need in the industry for PSA products that can have little or no organic solvents such as BTX. Silicone compositions that cure to form silicone PSA typically contain a polyorganosiloxane gum and a polyorganosilicate resin.

[0004] Polyorgano-silicate resins are typically produced in aromatic solvents because the resin is solid at room temperature (RT). Without a solvent, the resin typically has a powder or flake form, which has a very low bulk density and can be difficult to store and transport. The powder can be inconvenient to handle and transport in the manufacturing process of silicone compositions such as silicone curable pressure-sensitive adhesive compositions. And the flake resin typically has a high glass transition temperature and a high melting temperature, which makes it difficult to blend homogeneously with other components, especially polyorganosiloxane gum, when preparing a silicone composition.

[0005] Pellets are a widely used form of starting material supply in the plastics industry. Pellets packed at high density can be easily stored, transported, and conveyed by common machinery such as belt feeders or screw feeders. However, the use of pellets is limited in the silicone industry.

[0006] Attempts in the past to produce pellets containing siloxane resins and polydiorganosiloxane polymers have involved dissolving the resin in a solvent or combining the resin and the polymer in a solvent and then removing the solvent. The resulting combination essentially contains residual solvent. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] Therefore, in the silicone industry, especially in the silicone pressure-sensitive adhesive industry, there is a need for a pellet-shaped polyorgano-silicate resin that is easy to transport and store in terms of both manufacturing process efficiency and mixing efficiency when combining polyorgano-silicate resin with other starting materials for products such as silicone curable pressure-sensitive adhesive compositions. A process for producing such pellets and using them to form a silicone pressure-sensitive adhesive-based aqueous dispersion that contains no or only a small amount of organic solvents such as BTX is desirable.

Means for Solving the Problem

[0008] A process for preparing solvent - free polyorganosiloxane pellets and a silicone pressure - sensitive adhesive - based aqueous dispersion prepared using the pellets are disclosed. This process involves 1) An extruder comprising a barrel having a first supply port, a second supply port, and an outlet with a die, heating means configured to heat the barrel, and a screw mechanism housed within the barrel, wherein the first supply port and the second supply port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first supply port and the second supply port towards the outlet, the first supply port is upstream of the second supply port, and the second supply port is upstream of the outlet, providing an extruder; 2) i) Adding at least a portion of a solvent - free polydiorganosiloxane gum through the first supply port into the extruder; and ii) adding a solvent - free polyorganosilicate resin through the second supply port into the extruder, wherein the gum and the resin are added in amounts such that the weight ratio of resin:gum is 2.1:1 to 5:1; 3) Mixing the solvent - free polydiorganosiloxane gum and the solvent - free polyorganosilicate resin within the barrel while heating the barrel at a temperature of 200 °C to 250 °C, thereby forming a mixture; 4) Transporting the mixture through the die of the outlet, thereby forming a strand; 5) Cooling the strand exiting the die; 6) Crushing the strand, thereby preparing solvent - free polyorganosiloxane pellets; 7) Supplying to a dispersing device the pellets prepared in step 6), a surfactant, water, and starting materials including an optionally additional amount of polydiorganosiloxane gum sufficient to adjust the resin:gum ratio to 0.4:1 to 3:1; 8) Mixing and heating the starting materials from step 7) in a dispersing device, thereby producing an aqueous dispersion of a silicone pressure-sensitive adhesive base.

[0009] A process for preparing an aqueous dispersion of a silicone pressure-sensitive adhesive composition includes performing a process for preparing an aqueous dispersion of a silicone pressure-sensitive adhesive base and combining the aqueous dispersion of the silicone pressure-sensitive adhesive base with additional starting materials including an initiator. The aqueous dispersion of the silicone pressure-sensitive adhesive composition can be used in a process including coating the aqueous dispersion of the silicone pressure-sensitive adhesive composition on a surface substrate and curing to form an adhesive article.

Brief Description of the Drawings

[0010]

Figure 1(A)

Figure 1(B)

Figure 1(C)

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0011] The solvent-free polyorganosiloxane pellets (pellets) prepared in the above process contain a polydiorganosiloxane gum (gum) and a polyorganosilicate resin (resin). Alternatively, the pellets may consist essentially of the gum and the resin. Alternatively, the pellets may consist of the gum and the resin. The amounts of the gum and the resin in the pellets are sufficient to provide a resin:gum weight ratio (R:G ratio) of 2.1:1 to 5:1. Alternatively, the R:G ratio may be 2.1:1 to 4.5:1, or 2.4:1 to 4.0:1, or 3.0:1 to 4.0:1, or 2.1:1 to 3.5:1, or 2.4:1 to 3.0:1, or 2.4:1 to 2.9:1, or 2.7:1 to 2.9:1, or 2.4:1 to 2.5:1.

[0012] Gum The gum in the pellets can be a polydiorganosiloxane gum terminated with an aliphatic unsaturated group or a hydroxyl group. The gum has a number average molecular weight (Mn) of ≧150,000 g / mol, or 200,000 g / mol to 1,000,000 g / mol, or 300,000 g / mol to 800,000 g / mol, or 500,000 g / mol to 1,000,000 g / mol when measured by GPC according to the test method in Reference Example 1 starting from column 31 of U.S. Patent No. 9,593,209.

[0013] The gum has the unit formula (G-1):(R 3 R 2 2SiO 1 / 2 ) a (R 2 2SiO 2 / 2 ) b (R 2 SiO 3 / 2 ) c and in the formula, each R 2 is independently selected from the group consisting of an alkyl group having 1 to 18 carbon atoms and an aryl group having 6 to 18 carbon atoms, and each R 3is a curable group selected independently, with subscript a ≥ 2, subscript b > 1500, and subscript c ≥ 0, provided that the quantity (a + b + c) is sufficient to give the above-mentioned Mn to the gum. Alternatively, subscript a can be 2. Alternatively, subscript b can be 2500 - 8000, or 4000 - 6000, or 5300 - 6000, or 5400 - 5900. Alternatively, subscript c can be 0.

[0014] In unit formula (G-1), R 2 can be an alkyl group having 1 to 18 carbon atoms. Alternatively, each R 2 can have 1 to 12 carbon atoms, or 1 to 6 carbon atoms. "Alkyl" means a cyclic, branched or unbranched saturated monovalent hydrocarbon group. Alkyl is exemplified by, but not limited to, methyl, ethyl, propyl (e.g., iso-propyl and / or n-propyl), butyl (e.g., isobutyl, n-butyl, tert-butyl, and / or sec-butyl), pentyl (e.g., isopentyl, neopentyl, and / or tert-pentyl), hexyl, heptyl, octyl, nonyl, and decyl, and branched alkyl groups having 6 to 18 carbon atoms, and cyclic alkyl groups such as cyclopentyl and cyclohexyl. Alternatively, one or more examples of R 2 can be an aryl group. "Aryl" means a completely unsaturated cyclic hydrocarbon group. Aryl is exemplified by, but not limited to, cyclopentadienyl, phenyl, anthracenyl, and naphthyl. Monocyclic aryl groups can have 5 to 9 carbon atoms, or 6 to 7 carbon atoms, or 5 to 6 carbon atoms. Polycyclic aryl groups can have 10 to 17 carbon atoms, or 10 to 14 carbon atoms, or 12 to 14 carbon atoms. Alternatively, each R 2 can be independently selected from methyl and phenyl. Alternatively, each R 2 can be alkyl. Alternatively, each R 2 can be methyl.

[0015] In unit formula (G-1), each R3 is a curable group. Each R 3 may independently be selected from the group consisting of OH and monovalent aliphatic unsaturated hydrocarbon groups having 2 to 18 carbon atoms. Alternatively, the aliphatic unsaturated hydrocarbon group of R 3 may have 2 to 12 carbon atoms, or 2 to 6 carbon atoms. Suitable monovalent aliphatic unsaturated hydrocarbon groups include alkenyl groups and alkynyl groups. "Alkenyl" means a monovalent hydrocarbon group having one or more carbon-carbon double bonds. The alkyl group may be linear, branched, or cyclic. Suitable alkenyl groups are exemplified by vinyl; allyl; propenyl (e.g., isopropenyl, and / or n-propenyl); and butenyl, pentenyl, hexenyl, and heptenyl (including branched isomers having 4 to 7 carbon atoms); and cyclohexenyl. "Alkynyl" means a monovalent hydrocarbon group having one or more carbon-carbon triple bonds. The alkynyl group may be branched, unbranched, or cyclic. Suitable alkynyl groups are exemplified by ethynyl, propynyl, and butynyl (including branched isomers having 2 to 4 carbon atoms). Alternatively, the aliphatic unsaturated group of R 3 may be an alkenyl such as vinyl, allyl, or hexenyl.

[0016] Alternatively, each R 2 may be an alkyl group, each R 3 may independently be selected from the group consisting of OH and alkenyl groups having 2 to 18 carbon atoms, subscript a may be 2, subscript c may be 0, and subscript b may be 5300 to 6000. Alternatively, each R 2 may be methyl, each R 3 may independently be selected from the group consisting of OH, vinyl, allyl, and hexenyl, subscript a may be 2, subscript c may be 0, and subscript b may be 5400 to 5900.

[0017] Alternatively, the gum may be a bis-hydroxyl terminated polydiorganosiloxane. The hydroxyl functional polydiorganosiloxane has the unit formula (G-2): [R 2 2(HO)SiO1 / 2 2(R 2 2SiO 2 / 2 ) d may have, wherein each R 2 is as described above, and the subscript d ≧ 0, provided that the subscript d has a value sufficient to impart the above Mn to the gum. Alternatively, the gum may be a bis-alkenyl terminated polydiorganosiloxane. The bis-alkenyl terminated polydiorganosiloxane may have the unit formula (G-3):(R 2 2R 3’ SiO 1 / 2 )2(R 2 2SiO 2 / 2 ) d may have, wherein each R 2 is as described above, R 3’ is an alkenyl group as described above, and the subscript d ≧ 0, provided that the subscript d has a value sufficient to impart the above Mn to the gum. Alternatively, the gum may be a combination of a bis-hydroxyl terminated polydiorganosiloxane and a bis-alkenyl terminated polydiorganosiloxane.

[0018] Gums are known in the art and can be prepared by methods such as hydrolysis and condensation of the corresponding organohalosilanes, or equilibration of cyclic polydiorganosiloxanes. Gums are commercially available; for example, SILASTIC™ SGM-36 is commercially available from Dow Silicones Corporation (Midland, Michigan, USA). Examples of gums suitable for use herein are: i) dimethylvinylsiloxy-terminated polydimethylsiloxane, ii) dimethylvinylsiloxy-terminated poly(dimethylsiloxane / methylphenyl)siloxane, iii) dimethylvinylsiloxy-terminated poly(dimethylsiloxane / diphenyl)siloxane, iv) phenyl, methyl, vinyl-siloxy-terminated polydimethylsiloxane, v) dimethylhexenylsiloxy-terminated polydimethylsiloxane, vi) dimethylhexenyl-siloxane-terminated poly(dimethylsiloxane / methylphenyl)siloxane, vii) dimethylhexenylsiloxy-terminated poly(dimethylsiloxane / diphenyl)siloxane, viii) hydroxyl-terminated polydimethylsiloxane, ix) hydroxyl-terminated poly(dimethylsiloxane / methylphenyl)siloxane, x) hydroxyl-terminated poly(dimethylsiloxane / diphenyl)siloxane, xi) exemplified by a combination of two or more of i) to x). Alternatively, the gum can be selected from the group consisting of i) dimethylvinylsiloxy-terminated polydimethylsiloxane, v) dimethylhexenylsiloxy-terminated polydimethylsiloxane, and combinations of i) and v). Alternatively, the gum can be selected from the group consisting of viii), ix), and x). Alternatively, the gum can be selected from the group consisting of i) and viii).

[0019] Polyorganosilicate resin The polyorganosilicate resin (resin) contains monofunctional units of the formula R M 3SiO 1 / 2 and tetrafunctional units of the formula SiO 4 / 2 ("Q" units), wherein each R M is an independently selected monovalent hydrocarbyl group. R MSuitable monovalent hydrocarbon groups can have 1 to 20 carbon atoms, or 1 to 12 carbon atoms, or 1 to 8 carbon atoms, or 1 to 4 carbon atoms, or 1 to 2 carbon atoms. Alternatively, R M The hydrocarbyl group of can be selected from the group consisting of alkyl groups, alkenyl groups, and aryl groups, alternatively the group consisting of alkyl and aryl, alternatively the group consisting of alkyl and alkenyl, alternatively the group consisting of alkyl. The alkyl group and the aryl group are as described above for R 2 , and the alkenyl group is as described above for the alkenyl group of R 3 . Alternatively, in the resin, each R M can be independently selected from the group consisting of alkyl, alkenyl, and aryl. Alternatively, each R M can be selected from methyl, vinyl, and phenyl. Alternatively, at least one-third, alternatively at least two-thirds of the R M groups are methyl groups. Alternatively, the monofunctional unit can be exemplified by (Me3SiO 1 / 2 ), (Me2PhSiO 1 / 2 ), and (Me2ViSiO 1 / 2 ). The resin is soluble in a solvent such as a starting material (H) exemplified by liquid hydrocarbons such as benzene, toluene, xylene, and heptane as described herein, or soluble in a liquid organosilicon compound such as a low-viscosity linear and cyclic polydiorganosiloxane.

[0020] When prepared, the resin contains the above monofunctional units and tetrafunctional units, the polyorganosiloxane further contains units having silanol (silicon-bonded hydroxyl) groups, and may also contain a neopentamer of the formula Si(OSiR M 3)4, wherein R M is as described above. As described in Reference Example 2 in column 32 of U.S. Patent No. 9,593,209, Si 29The molar ratio of M and Q units can be measured using Nuclear Magnetic Resonance (NMR) spectroscopy, where the ratio is expressed as {M(resin) + (M(neopentamer)} / {Q(resin) + Q(neopentamer)}, representing the molar ratio of the total number of triorganosiloxy groups (monofunctional units) in the resin and neopentamer portions of the polyorganosilicate resin to the total number of silicate groups (Q units) in the resin and neopentamer portions.

[0021] The Mn of the resin depends on various factors including the types of hydrocarbon groups represented by R M When the peak representing the neopentamer is excluded from the measurement, the Mn of the resin refers to the number average molecular weight measured using GPC according to the procedure in Reference Example 1 in Column 31 of US Patent No. 9,593,209. The Mn of the resin can be greater than 2,000 g / mol, or can be 2,500 g / mol to 15,000 g / mol. Alternatively, the Mn of the resin can be 2,000 g / mol to 8,000 g / mol, or 2,900 g / mol to 6,000 g / mol, or 2,900 to 5,000 g / mol.

[0022] The resin can be prepared by any suitable method such as the co-hydrolysis of the corresponding silanes or the silica hydrosol capping method. The resin can be prepared by the silica hydrosol capping method such as those disclosed in US Patent No. 2,676,182 to Daudt et al., US Patent No. 4,611,042 to Rivers-Farrell et al., and US Patent No. 4,774,310 to Butler et al. The above-mentioned method of Daudt et al. involves reacting a silica hydrosol under acidic conditions with a hydrolyzable triorganosilane such as trimethylchlorosilane, a siloxane such as hexamethyldisiloxane, or a mixture thereof, and recovering a copolymer having monofunctional units and tetrafunctional units. The resulting copolymer generally contains 2 to 5 weight percent hydroxyl groups.

[0023] The intermediates used to prepare the resin can be triorganosilanes and silanes having four hydrolyzable substituents, or alkali metal silicates. The triorganosilane can have the formula, R M 3SiX 1 , where R M is as described above and X 1 represents a hydrolyzable substituent. The silane having four hydrolyzable substituents can have the formula SiX 2 4, where each X 2 is halogen, alkoxy, or hydroxyl. Suitable alkali metal silicates include sodium silicate.

[0024] The resin prepared as described above typically contains silicon-bonded hydroxyl groups, for example, of the formula HOSi 3 / 2 and / or HOR M 2SiO 1 / 2 . The polyorganosilicate resin can contain up to 5 wt%, or on the same basis up to 2 wt%, of silicon-bonded hydroxyl groups. The concentration of silicon-bonded hydroxyl groups present in the resin can be determined using Fourier transform infrared (FTIR) spectroscopy in accordance with ASTM standard E-168-16. For certain applications, it may be desirable for the amount of silicon-bonded hydroxyl groups to be less than 0.7%, or less than 0.3%, or less than 1%, or between 0.3% and 0.8%. The silicon-bonded hydroxyl groups formed during the preparation of the resin can be converted to trihydrocarbylsiloxane groups or different hydrolyzable groups by reacting the resin with a silane, disiloxane, or disilazane containing a suitable end group. The silane containing a hydrolyzable group can be added in a molar excess over the amount necessary to react with the silicon-bonded hydroxyl groups on the resin.

[0025] Alternatively, the resin can further contain units of 2% or less, or 0.7% or less, or 0.3% or less, or between 0.3% and 0.8%, represented by the formula XSiO 3 / 2 and / or XR M 2SiO 1 / 2 , where R M is as described above and X is X1 represents a hydrolyzable substituent as described above.

[0026] Alternatively, the resin may have a terminal aliphatic unsaturated group. A resin having a terminal aliphatic unsaturated group can be prepared by reacting a Daudt et al. product with an unsaturated organic group-containing end-capping agent and an aliphatic unsaturated-free end-capping agent in an amount sufficient to provide 3 to 30 mole percent of unsaturated organic groups in the final product. Examples of end-capping agents include, but are not limited to, silazanes, siloxanes, and silanes. Suitable end-capping agents are known in the art and are exemplified in U.S. Patent Nos. 4,584,355, 4,591,622, and 4,585,836. Such resins can be prepared using a single end-capping agent or a mixture of such agents.

[0027] Alternatively, the resin may have the unit formula (R-1): (R 1 R 2 2SiO 1 / 2 ) w (R 2 3SiO 1 / 2 ) x (SiO 4 / 2 ) y X z and may contain, where R 2 and X are as described above, each R 1 is an independently selected aliphatic unsaturated group having 2 to 18 carbon atoms (e.g., those as described above for R 3 ), and the subscripts w, x, y, and z have average values such that w≥0, x≥0, y>1, z≥0, and the amount (w + x)>4. Alternatively, each R 2 in the unit formula (R-1) can be alkyl or methyl. The amount (w + x + y + z) is sufficient to give the resin a weight average molecular weight of 2,000 g / mol to 15,000 g / mol, or 8,000 to 10,000, or 9,000 to 9,500. Alternatively, each R 1may be independently selected from the group consisting of vinyl, allyl, and hexenyl. Alternatively, each X may be OH. Alternatively, the subscript x may be 40 - 55, or 43 - 50. Alternatively, the subscript y may be 45 - 65, or 50 - 57. Alternatively, the subscript z may be 0 up to a value sufficient to provide a resin having up to 5 wt% OH groups, or up to 2 wt%, or up to 0.7 wt% OH groups. Alternatively, the resin has a unit formula (R-2):(R 2 3SiO 1 / 2 ) v (SiO 4 / 2 ) y X z and may contain, where R 2 , X, subscript y, and subscript z are as described above, and subscript v > 4.

[0028] The above resin can be prepared in a solvent and then devolatilized. For example, the resin can be dried by heating to a temperature of up to 150 °C to remove the solvent without degrading the resin. For example, the resin can be optionally heated under reduced pressure to remove the solvent. The solvent-free polyorganosilicate resin contains, for example, undetectable, or 0 - 2%, or 0% - 1%, or 0 ppm - 100 ppm of residual solvent from the resin manufacturing process. In a method for preparing pellets, the solvent-free polyorganosilicate resin used can be in the form of a powder or flakes.

[0029] Method for preparing solvent-free polyorganosiloxane pellets The solventless polyorganosiloxane pellets (pellets) contain the above-mentioned resin and gum. The pellets are solventless, and as used herein, the term "solventless" means that no solvent is intentionally added during the production of the pellets. Those skilled in the art will recognize that although polyorganosilicate resins can be prepared by the use of solvents, the solventless polyorganosilicate resin used in this method is devolatilized as described above to remove the solvent, and no solvent is added during the process of making the pellets. The solventless polyorganosilicate resin can be supplied to the extruder as flakes or powder.

[0030] The process for preparing the above pellets is 1) An extruder comprising a barrel having a first feed port, a second feed port, and an outlet having a die, heating means configured to heat the barrel, and a screw mechanism housed within the barrel, wherein the first feed port and the second feed port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first feed port and the second feed port towards the outlet, the first feed port is upstream of the second feed port, and the second feed port is upstream of the outlet, providing an extruder. 2) i) Adding at least a portion of the gum as described above through the first feed port into the extruder, and ii) adding the resin as described above through the second feed port into the extruder, wherein the gum and the resin are added in amounts such that the weight ratio of resin:gum is 2.1:1 to 5:1. 3) Mixing the gum and the resin within the barrel while heating the barrel at a temperature of 200°C to 250°C, thereby forming a mixture. 4) Transporting the mixture through the die of the outlet, thereby forming a strand. 5) Cooling the strand exiting the die. 6) Crushing the strand, thereby preparing the pellets, and includes.

[0031] The above method may optionally further include, before step 2), preparing a solvent-based polyorganosilicate resin and devolatilizing the solvent-based polyorganosilicate resin to form a solvent-free polyorganosilicate resin.

[0032] In the above method, all of the gum can be added to the first feed port. Alternatively, up to 15% of the gum can be added to the second feed port (e.g., in a blend with the resin).

[0033] Steps 5) and 6) can be carried out continuously or simultaneously. For example, steps 5) and 6) can be carried out simultaneously (i.e., in one device) such as in a water bath pelletizer. Alternatively, steps 5) and 6) can be carried out continuously using separate devices such as a water bath for cooling the strands in step 5) and a separate pelletizer in step 6). Commercially available devices can be used to carry out the above method. Extruders such as twin-screw extruders and pelletizing devices are known in the art and are commercially available. The pellets obtained by preparing as described above are useful for preparing an aqueous dispersion based on a silicone pressure-sensitive adhesive.

[0034] Process for producing an aqueous dispersion based on a silicone pressure-sensitive adhesive The above pellets can be used in a process for producing an aqueous dispersion based on a silicone pressure-sensitive adhesive. This process comprises performing a process including the above steps 1) to 6) to thereby prepare pellets, 7) feeding to a dispersing device starting materials comprising the pellets prepared in step 6), an additional amount of polydiorganosiloxane gum sufficient to adjust the resin:gum ratio to 0.4:1 to 2:1, a surfactant, and water, 8) mixing and heating the starting materials from step 7) in the dispersing device to thereby produce an aqueous dispersion based on a silicone pressure-sensitive adhesive. This process may further include collecting the aqueous dispersion based on a silicone pressure-sensitive adhesive when it exits the dispersing device.

[0035] Step 7) can be carried out in conventional continuous process equipment for preparing an aqueous siloxane dispersion. Illustrative examples of continuous mixers / compounders include single-screw extruders, twin-screw extruders, and multi-screw extruders, co-rotating extruders, and counter-rotating twin-screw extruders, two-stage extruders, twin-screw rotary continuous mixers, dynamic or static mixers, or combinations of these types of equipment, such as those manufactured by Krupp Werner & Pfleiderer Corp (Ramsey, NJ) and Leistritz (NJ). Alternatively, the dispersing device used in Step 7) can be an extruder, or a twin-screw extruder.

[0036] If an extruder is used in Step 7) of the process for making an aqueous dispersion based on a silicone pressure-sensitive adhesive, the extruder can be the same as the extruder used to make the above pellets. Alternatively, a different extruder can be used in Step 7) of the process for making an aqueous dispersion based on a silicone pressure-sensitive adhesive. The extruder used to make an aqueous dispersion based on a silicone pressure-sensitive adhesive can comprise a barrel having one or more inlets spaced along the barrel, a screw mechanism housed within the barrel, and an outlet optionally fitted with a backpressure regulator. The screw mechanism can mix the starting materials and convey them from the inlets towards the outlet. This extruder can further comprise heating means configured to heat the barrel. The inlets are configured to introduce the starting materials into the extruder. The extruder can optionally further comprise a backpressure regulator at the outlet to control the pressure inside the extruder. Step 7) and / or Step 8) can be carried out at a temperature of 50°C to 200°C, or 70°C to 150°C.

[0037] Additional gum Additional polydiorganosiloxane gum can be added in step 7) to adjust the resin:gum ratio from the pellets to a value suitable for the silicone pressure-sensitive adhesive composition. The additional polydiorganosiloxane gum is as described above, and the additional polydiorganosiloxane gum selected may be the same as or different from the polydiorganosiloxane gum used to prepare the pellets. The amount of additional polydiorganosiloxane gum added is sufficient to provide an aqueous dispersion based on a silicone pressure-sensitive adhesive having a resin:gum ratio of 0.4:1 to 3:1, or 0.4:1 to 2:1, or 0.5:1 to 1.9:1, or 0.7:1 to 1.8:1, or 0.9:1 to 1.7:1, or 1:1 to 1.5:1.

[0038] Surfactant The aqueous dispersion based on the silicone pressure-sensitive adhesive contains a surfactant. The surfactant can be solid or liquid. The solid surfactant can be delivered as an aqueous dispersion containing 25% to 75% solid surfactant (active). The surfactant can be supplied to the dispersing device together with the pellets. Alternatively, the surfactant can be supplied to the dispersing device together with water. Alternatively, the surfactant can be supplied to the dispersing device separately from the other starting materials. The surfactant is selected from the group consisting of anionic surfactants, nonionic surfactants, and combinations of both anionic and nonionic surfactants, provided that the surfactant does not include sulfonic acids and their salt derivatives, long-chain carboxylic acid surfactants and their salts, fatty acid amines and amides, and their salts and derivatives, alkyl glucosides, and linear silicone polyethers.

[0039] Examples of anionic surfactants include alkyl sulfates having at least 6 carbon atoms in the alkyl substituent, such as sodium lauryl sulfate, and sulfate esters of polyoxyethylene monoalkyl ethers. Some other examples of anionic surfactants are alkali metal sulfosuccinates; sulfonated glyceryl esters of fatty acids (e.g., sulfonated monoglyceride of coconut fatty acid); monovalent sulfonated alcohol ester salts (e.g., sodium oleyl isocyanate); sulfonated products of fatty acid nitriles (e.g., palmitonitrile sulfonate); sulfonated aromatic hydrocarbons (e.g., sodium α-naphthalene monosulfonate); condensation products of naphthalene sulfonic acid with formaldehyde; sodium octahydroanthracene sulfonate; alkali metal alkyl sulfates; ether sulfates having an alkyl group of 8 or more carbon atoms, such as sodium lauryl ether sulfate, and alkylaryl sulfonates having one or more alkyl groups of 8 or more carbon atoms.

[0040] Examples of commercially available anionic surfactants that can be used include the sodium salt of an alkyl alkoxylate sulfate sold under the trade name DOWFAX™ AS-801 by The Dow Chemical Company (Midland, Michigan, USA), sodium n-hexadecyl diphenyloxide disulfonate sold under the trade name DOWFAX™ 8390 by The Dow Chemical Company (Midland, Michigan), and the sodium salt of a secondary alkane sulfonate sold under the trade name HOSTAPUR™ SAS 60 by Clariant Corporation (Charlotte, North Carolina).

[0041] Some suitable nonionic surfactants that can be used include polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, and polyoxyethylene sorbitan fatty acid esters. Commercially available nonionic surfactants include (i) 2,6,8-trimethyl-4-nonyl polyoxyethylene ether sold under the trade name TERGITOL™ TMN-10, (ii) C11-15 secondary alkyl polyoxyethylene ethers sold by Dow Chemical Company (Midland, Michigan, USA) under the trade names TERGITOL™ 15-S-9, TERGITOL™ 15-S-15, TERGITOL™ 15-S-30, and TERGITOL™ 15-S-40, octyl phenyl polyoxyethylene (40) ether sold by Dow Chemical Company under the trade name TRITON™ X405, (iii) nonyl phenyl polyoxyethylene (10) ether sold by Stepan Company under the trade name MAKON™ 10, (iv) ethoxylated alcohol sold by Henkel Corp. / Emery Group (Cincinnati, Ohio, USA) under the trade name Trycol 5953, (v) ethoxylated alcohols sold by Croda Inc. (Edison, New Jersey, USA) under the trade names BRIJ™ L23 and BRIJ™ L4, (vi) alkyl oxo alcohol polyglycol ethers (e.g., GENAPOL™ UD050 and GENAPOL™ UD110), (vii) compositions such as C10 Guerbet alcohol and alkyl polyethylene glycol ethers based on ethylene oxide (e.g., LUTENSOL™ XP79).

[0042] Suitable nonionic surfactants also include poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers. Poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers are also commonly known as poloxamers. This is a nonionic triblock copolymer consisting of a hydrophobic chain of polyoxypropylene (poly(propylene oxide)) in the central part and two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)) on both sides thereof. Poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers are commercially available from BASF (Florham Park, New Jersey, USA) and are sold under the trade names of PLURONIC (trademark) such as L61, L62, L64, L81, P84, etc.

[0043] Other suitable nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene lauryl ether, polyoxyethylene sorbitan monooleate, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester, polypropylene glycol, diethylene glycol, ethoxylated trimethylnonanol, and polyoxyalkylene glycol-modified polysiloxane surfactants. Commercially available nonionic surfactants that can be used include 2,6,8-trimethyl-4-nonyloxypolyethylene oxyethanol sold under the trade name TERGITOL (trademark) TMN-10, alkylene oxy polyethylene oxyethanol (C 11~15 secondary alcohol ethoxylate 7EO, 9EO, and 15EO) sold under the trade names TERGITOL (trademark) 15-S-7, TERGITOL (trademark) 15-S-9, TERGITOL (trademark) 15-S-15; other C sold under the trade names ECOSURF (trademark) EH-40, and TERGITOL (trademark) 15-S-12, 15-S-20, 15-S-30, and 15-S-4011~15 Compositions such as secondary alcohol ethoxylates, octylphenoxypolyethoxyethanol (40 EO) sold under the trademark TRITON™ X-405, and alcohol ethoxylates bearing the trademark ECOSURF™ EH such as ECOSURF™ EH-40 are included. All of these surfactants are sold by the Dow Chemical Company.

[0044] Commercially available, other useful nonionic surfactants are nonylphenoxypolyethoxyethanol (10 EO) sold under the trademark MAKON™ 10 by Stepan Company, polyoxyethylene 23 lauryl ether (Laureth-23) sold under the trademark BRIJ™ 35L by ICI Surfactants (Wilmington, Delaware, USA), and polyoxyethylene ether alcohol, RENEX™ 30, further sold by ICI Surfactants.

[0045] Suitable nonionic surfactants also include poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers. Poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers are also generally known as poloxamers. This is a nonionic triblock copolymer consisting of a hydrophobic chain of polyoxypropylene (poly(propylene oxide)) in the central part and two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)) on both sides. Poly(oxyethylene)-poly(oxypropylene)-poly(oxyethylene) triblock copolymers are commercially available from BASF (Florham Park, NJ) and are sold under the trademark PLURONIC™ such as PLURONIC™ L61, L62, L64, L81, P84.

[0046] Other useful commercial nonionic surfactants include nonylphenoxypolyethoxyethanol (10 EO) sold under the trademark MAKON® 10 by Stepan Company (Northfield, Illinois), polyoxyethylene 23 lauryl ether (Laureth-23) sold under the trademark BRIJ® 35L by ICI Surfactants (Wilmington, Delaware), and polyoxyethylene ether alcohol, RENEX® 30, sold by ICI Surfactants (Wilmington, Delaware).

[0047] The nonionic surfactant can also be a silicone polyether (SPE). The SPE can be a polyorganosilicate resin having a polyether group bonded to a silicon atom therein. Suitable SPEs include DOWSIL® 2-3216 INT from Dow Silicones Corporation (Midland, Michigan, USA).

[0048] Alternatively, the nonionic surfactant can include a polyvinyl alcohol compound. Polyvinyl alcohol compounds are known in the art and are disclosed, for example, in paragraphs

[0172] and

[0173] of US Patent Application Publication No. 2007 / 0099007. The polyvinyl alcohol compound may be made by saponification of polyvinyl acetate, so up to 15% of the polyvinyl acetate may remain in the polyvinyl alcohol compound used herein. Alternatively, the polyvinyl alcohol compound can be 88% - 92% polyvinyl alcohol (in equilibrium with 12% - 8% polyvinyl acetate). The polyvinyl alcohol compound can have a minimum viscosity of 5 cP in a 4% aqueous solution at 20°C.

[0049] The surfactant used in the process described herein can be one surfactant or a combination of two or more surfactants. The amount of the surfactant depends on various factors including the type and amount of the surfactant selected, but the amount of the surfactant can be sufficient to provide from 0.1% to 20%, or alternatively from 0.5% to 10%, based on the total weight of the resin and gum.

[0050] Water Water is generally not limited and can utilize undiluted (i.e., without any carrier vehicle / solvent) and / or pure (i.e., free or substantially free of minerals and / or other impurities) water. For example, the water may be treated or untreated prior to use in the above process. Examples of processes that can be used to purify water include distillation, filtration, deionization, and combinations of two or more thereof, whereby the water may be deionized, distilled, and / or filtered. Alternatively, the water may be untreated (e.g., it can be tap water or well water provided by a municipal water system that is used without further purification). Alternatively, the water can be purified prior to use in the process.

[0051] Water can be utilized in any amount selected by one of ordinary skill in the art depending on various factors, such as the desired dilution of the silicone pressure-sensitive adhesive composition to be prepared. Alternatively, the amount of water in the aqueous dispersion of the silicone pressure-sensitive adhesive base can be from 10% to 95%, or alternatively from 30% to 70%, based on the total weight of all starting materials in the aqueous dispersion of the silicone pressure-sensitive adhesive base.

[0052] Process for preparing an aqueous dispersion of a silicone pressure-sensitive adhesive composition A silicone pressure-sensitive adhesive-based aqueous dispersion can be used in a process for preparing an aqueous dispersion of a silicone pressure-sensitive adhesive composition. This method involves performing a process including the above steps 1) to 8) to form a silicone pressure-sensitive adhesive-based aqueous dispersion, and 9) mixing the silicone pressure-sensitive adhesive-based aqueous dispersion with additional starting materials selected from the group consisting of a free radical initiator, a solvent, a coating additive, and combinations thereof, thereby forming an aqueous dispersion of a silicone pressure-sensitive adhesive composition. Step 9) can be carried out by any convenient means using batch, semi-continuous, or continuous processing. The continuous process equipment discussed above for step 7) can be used. Alternatively, the mixing in step 9) can be carried out in batch, semi-continuous, or continuous mode. Batch equipment with high-shear and high-speed dispensers, such as those made by Charles Ross & Sons (NY), Hockmeyer Equipment Corp. (NJ), batch mixing equipment such as those sold under the trade name Speedmixer™, and batch equipment with high-shear action, such as Banbury type (CW Brabender Instruments Inc., NJ) and Henschel type (Henschel mixers America, TX), can be used and are commercially available. Alternatively, the mixing in step 9) can be carried out using, for example, batch mixing equipment with medium / low shear, such as a change-can mixer, a double planetary mixer, a conical shaft mixer, a ribbon blender, a double arm mixer, or a sigma blade mixer. Coating additives are exemplified by defoamers, wetting agents, pH adjusting additives, and combinations of two or more of them.

[0053] Free radical initiator The free radical initiator may include organic peroxide compounds such as alkyl peroxides, diacyl peroxides, peroxide esters, and / or peroxide carbonates. Suitable organic peroxide compounds include benzoyl peroxide; 4-monochlorobenzoyl peroxide; dicumyl peroxide; tert-butyl peroxybenzoate; tert-butyl cumyl peroxide; tert-butyl oxide 2,5-dimethyl-2,5-di-tert-butylperoxyhexane; 2,4-dichlorobenzoyl peroxide; di-tert-butyl peroxy-diisopropylbenzene; 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane; 2,5-di-tert-butylperoxyhexane-3,2,5-dimethyl-2,5-bis(tert-butylperoxy)hexane, or cumyl-tert-butyl peroxide. Suitable peroxide compounds are known in the art and are disclosed, for example, in paragraph

[0093] of US Patent Application Publication No. 2018 / 0105692.

[0054] The amount of free radical initiator added in step 9) depends on various factors including the type and amount of initiator selected and the selection of other starting materials, but the initiator can be added in an amount of 1% to 10%, or 2% to 6%, or 2% to 5% based on the total weight of the resin and gum.

[0055] Solvent Optionally, in step 7) and / or step 9) described below, a solvent can be added to the aqueous dispersion of the silicone pressure-sensitive adhesive composition. Without being bound by theory, it is believed that the solvent can assist in the mixing and / or delivery of one or more of the starting materials. For example, the initiator can be dissolved or dispersed in the solvent to facilitate mixing. Suitable solvents include polyalkylsiloxanes and / or organic solvents such as alcohols, ketones, aromatic hydrocarbons, aliphatic hydrocarbons, glycol ethers, tetrahydrofuran, mineral spirits, naphtha, tetrahydrofuran, mineral spirits, naphtha, or combinations thereof. Polyalkylsiloxanes having a suitable vapor pressure can be used as solvents, and these include hexamethyldisiloxane, octamethyltrisiloxane, hexamethylcyclotrisiloxane, and other low molecular weight polyalkylsiloxanes such as DOWSIL (trademark) 200 Fluids and DOWSIL (trademark) OS FLUIDS with a viscosity of 0.5 - 1.5 cSt, commercially available from Dow Silicones Corporation (Midland, Michigan, U.S.A.).

[0056] Alternatively, an organic solvent can be used. The organic solvent can be an alcohol such as methanol, ethanol, isopropanol, butanol, or n-propanol; a ketone such as acetone, methyl ethyl ketone, or methyl isobutyl ketone; an aromatic hydrocarbon such as benzene, toluene, or xylene; an aliphatic hydrocarbon such as heptane, hexane, or octane; a glycol ether such as propylene glycol methyl ether, dipropylene glycol methyl ether, propylene glycol n-butyl ether, propylene glycol n-propyl ether, or ethylene glycol n-butyl ether, tetrahydrofuran; mineral spirits; naphtha; or combinations thereof.

[0057] The amount of solvent will depend on various factors including the type of solvent selected for the aqueous dispersion of the silicone pressure-sensitive adhesive composition, as well as the amount and type of other starting materials selected. However, the amount of solvent can be 0% to <10%, or 0% to <2%, or 0% to <1%, or 0% to <0.5% based on the total weight of all starting materials in the aqueous dispersion of the silicone pressure-sensitive adhesive composition. Alternatively, the solvent can be omitted.

[0058] Optional starting materials can also be added to the aqueous dispersion of the silicone pressure-sensitive adhesive composition prepared by the above process. Such optional starting materials include, for example, defoamers, wetting agents, pH adjustment additives, and combinations of two or more thereof. Other optional starting materials include, for example, reactive diluents, fragrances, preservatives, fillers such as silica, quartz, or chalk, and combinations of two or more thereof.

[0059] Alternatively, the curable silicone pressure-sensitive adhesive composition may not contain a filler or may contain a filler only in a limited amount such as 0 to 30% by weight of the curable silicone pressure-sensitive adhesive composition. The filler can agglomerate or otherwise adhere to the coater equipment used to apply the curable silicone pressure-sensitive adhesive composition to the substrate. The filler can also interfere with the optical properties, such as transparency, of the silicone pressure-sensitive adhesive and / or any tape formed therefrom.

[0060] Method of Use Using an aqueous dispersion of the silicone pressure-sensitive adhesive composition prepared as described above, an adhesive article, for example, a silicone pressure-sensitive adhesive (prepared by curing the above curable silicone pressure-sensitive adhesive composition), can be formed on a substrate. The adhesive article can be prepared by a process including preparing an aqueous dispersion of the silicone pressure-sensitive adhesive composition by performing the above process, coating the aqueous dispersion of the silicone pressure-sensitive adhesive composition on the surface of the substrate, and curing the silicone pressure-sensitive adhesive composition to form a silicone pressure-sensitive adhesive. Before curing (and optionally during curing), the substrate can be dried to remove all or part of the water from the aqueous dispersion of the silicone pressure-sensitive adhesive composition, thereby leaving the silicone pressure-sensitive adhesive composition on the substrate.

[0061] To improve the bonding of the silicone pressure-sensitive adhesive to the substrate, this process can optionally further include treating the surface of the substrate before coating the aqueous dispersion of the silicone pressure-sensitive adhesive composition on the substrate. Treating the surface of the substrate can be carried out by any convenient means, such as applying a primer or subjecting the substrate to corona discharge treatment, etching, or plasma treatment before coating the aqueous dispersion of the silicone pressure-sensitive adhesive composition on the substrate.

[0062] Coating the silicone pressure-sensitive adhesive composition on the surface of the substrate can be carried out by any convenient means. For example, the curable silicone pressure-sensitive adhesive composition can be applied on the surface of the substrate by a gravure coater, an offset coater, an offset-gravure coater, a roller coater, a reverse roller coater, an air knife coater, or a curtain coater.

[0063] The substrate can be any material that can withstand the curing conditions (described herein) used to cure the silicone pressure-sensitive adhesive composition to form a silicone pressure-sensitive adhesive on the substrate. For example, any substrate that can withstand heat treatment at a temperature of 150 °C or higher, or at a temperature of 50 °C to 120 °C, is suitable. Examples of suitable materials for such substrates include plastic films such as polyimide (PI), polyetheretherketone (PEEK), polyethylene naphthalate (PEN), liquid crystal polyarylate, polyamideimide (PAI), polyether sulfide (PES), or polyethylene terephthalate (PET), or polyethylene (PE), or polypropylene (PP). Alternatively, the substrate can be a metal foil such as aluminum foil or copper foil. Alternatively, the substrate can also be paper such as kraft paper. The thickness of the substrate is not critical, but the thickness can range from 5 micrometers to 300 micrometers.

[0064] Drying can be carried out before and / or during curing. Drying can be carried out by heating at a temperature sufficient to evaporate water (and solvent if present), for example, 50°C to 120°C, to remove water and effect curing. Alternatively, drying can be carried out by heating for a time sufficient to remove all or part of the water (e.g., 30 seconds to 1 hour, or 1 minute to 5 minutes) at a temperature of 50°C to 120°C, or 50°C to 100°C, or 70°C to 80°C. The method further includes curing the silicone pressure-sensitive adhesive composition by heating at a temperature of room temperature or 80°C to 220°C, or 140°C to 220°C, or 150°C to 220°C, or 160°C to 200°C, or 165°C to 180°C for a time sufficient to cure the silicone pressure-sensitive adhesive composition (e.g., 30 seconds to 1 hour, or 1 minute to 5 minutes). If it is necessary to increase the curing rate or lower the process curing temperature, the initiator level can be increased. Thereby, a silicone pressure-sensitive adhesive is formed on the substrate. Drying and / or curing can be carried out by placing the substrate in an oven. The amount of the silicone pressure-sensitive adhesive composition applied to the substrate depends on the specific application, but the amount can be sufficient such that the thickness after curing of the silicone pressure-sensitive adhesive can be 5 micrometers to 200 micrometers.

[0065] The method described herein can optionally further include, for example, applying a removable release liner to the silicone pressure-sensitive adhesive on the opposite side of the substrate to protect the silicone pressure-sensitive adhesive before use of the adhesive article. The release liner can be applied before, during, or after curing of the curable silicone pressure-sensitive adhesive composition, or after curing.

Examples

[0066] These examples are intended to illustrate the invention to those skilled in the art and should not be construed as limiting the scope of the invention as claimed. The materials in Table 1 were used in these examples.

[0067]

Table 1

[0068] Example 1 - Apparatus and Procedure for Preparing Pellets Figure 1(A) shows an apparatus 110 for preparing pellets (Process A). The apparatus 110 included a twin - screw extruder (Leistritz ZSE27 MAXX with L / D = 48 and 12 steps) 100 upstream of a water - ring pelletizer 108. The twin - screw extruder 100 had a barrel 101 having a first feed port 102, a second feed port 103, and an outlet 104 with a die (not shown), heating means (not shown) configured to heat the barrel 101, and a screw mechanism (not shown) housed within the barrel 101. The first feed port 102 was configured to introduce gum into the extruder at the fourth stage 105. The second feed port 103 was configured to introduce a polyorganosilicate resin at the fifth stage 106. The screw mechanism was configured to mix and convey the gum and the resin from the first feed port 102 and the second feed port 103 through the die to the outlet 104, form a strand 107, and enter the water - ring pelletizer 108. The water - ring pelletizer was configured to cool and grind the strand 107 to form pellets and exit the extruder at an outlet 109.

[0069] All or part of the gum was supplied to the extruder 100 through the first supply port 102. All of the resin was supplied to the extruder 100 through the second supply port 103. For some samples where a portion of the gum was to be added via the first supply port 102, the remainder of the gum was added along with the resin via the second supply port 103. The barrel was heated to 200°C to 250°C. The gum added to the first supply port 102 was supplied at 2.5 kg / hour, and the resin (optionally including a portion of the gum) added to the second supply port 103 was supplied at 7.5 kg / hour. The gum and resin were mixed and conveyed to the outlet 104 through a die (not shown), thereby forming a strand 107. The strand entered the underwater pelletizer 108, was pulverized into pellets, and exited the apparatus 110 at the outlet 109. Table 2 below shows the formulations of the gum and resin used to form the pellets using this general procedure.

[0070] Table 2 below shows the composition of the pellets prepared using the procedure of Reference Example 1. The types of resin and gum are defined in Table 1. The amounts of resin and gum are in parts by weight.

[0071] [Table 2]

[0072] Comparative Example 2 Figure 1(B) shows an apparatus 210 for preparing pellets (Process B). The apparatus 210 is equipped with a twin-screw extruder (Leistritz ZSE27 MAXX having L / D = 48 and 12 steps) 200 upstream of the underwater pelletizer 208. The twin-screw extruder 200 has a barrel 201 having a first feed port 203, a second feed port 202, and an outlet 204 having a die (not shown), heating means (not shown) configured to heat the barrel 201, and a screw mechanism (not shown) housed within the barrel 201. The first feed port 203 was configured to introduce resin into the extruder at the first stage 206. The second feed port 202 was configured to introduce gum at the fourth stage 205. The screw mechanism was configured to mix and convey the resin and the gum from the first feed port 203 and the second feed port 202 through the die to the outlet 204, forming a strand 207 and entering the underwater pelletizer 208. The underwater pelletizer was configured to cool and grind the strand 207 to form pellets and exit the extruder at the outlet 209.

[0073] All of the resin was supplied to the extruder 200 through the first feed port 203. All or part of the gum was supplied to the extruder 200 through the second feed port 202. For some samples where a portion of the gum was added with the resin through the first feed port 203, the remainder of the gum was added through the second feed port 202. The barrel was heated to 200°C to 250°C. The gum added to the second feed port 202 was supplied at 2.5 kg / hour, and the resin (optionally including a portion of the gum) added to the first feed port 203 was supplied at 7.5 kg / hour. The gum and the resin were mixed and conveyed through a die (not shown) to the outlet 204, thereby forming a strand 207. The strand entered the underwater pelletizer 208, was ground into pellets, and exited the apparatus 210 at the outlet 209. Composition 1 of Table 2 above was used.

[0074] Figure 2(A) shows the pellets produced by the method of Example 1 using Composition No. 1 in Table 2. Figure 2(B) shows the pellets produced by the method of Comparative Example 2 using Composition No. 1 in Table 2. The pellets produced by the method of Comparative Example 2 were non-uniform in size, shape, and appearance. Without wishing to be bound by theory, Examples 1 and Comparative Example 2 show that the order of addition (i.e., adding at least 85% of the gum before adding the resin) provides an advantage in the method for making pellets herein, i.e., the pellets are believed to have a more uniform size and shape and an improved appearance using the claimed method.

[0075] Example 3 Figure 1(C) shows an apparatus 310 for preparing pellets (Process C). The apparatus 310 included a twin-screw extruder (Leistritz ZSE27 MAXX with L / D = 48 and 12 stages) 300 upstream of a water tank 311 upstream of an underwater pelletizer 308. The twin-screw extruder 300 had a barrel 301 with a first feed port 302, a second feed port 303, and an outlet 304 with a die (not shown), heating means (not shown) configured to heat the barrel 301, and a screw mechanism (not shown) housed within the barrel 301. The first feed port 302 was configured to introduce gum into the extruder at the fourth stage 305. The second feed port 303 was configured to introduce a polyorganosilicate resin at the fifth stage 306. The screw mechanism was configured to mix and convey the gum and the resin from the first and second feed ports 302 and 303 through the die to the outlet 304, form a strand 307, and enter the water tank 311 and then the underwater pelletizer 308. The underwater pelletizer 308 was configured to cool and grind the strand 307 to form pellets and exit the extruder at an outlet 309.

[0076] All or part of the gum was fed into extruder 300 through first feed port 302. All of the resin was fed into extruder 300 through second feed port 303. For some samples where part of the gum was to be added via first feed port 302, the remainder of the gum was added together with the resin via second feed port 303. The barrel was heated to 200°C to 250°C. The gum added to first feed port 302 was fed at 2.5 kg / hour, and the resin (optionally including a portion of the gum) added to second feed port 303 was fed at 7.5 kg / hour. The gum and resin were mixed and conveyed through a die (not shown) to outlet 304, thereby forming strand 307. The strand entered underwater pelletizer 308, was crushed into pellets, and exited apparatus 310 at outlet 309. Using the composition 1 of Table 2 above, pellets were prepared in the same manner as in Example 1 and Comparative Example 2. The pellets are shown in Figure 2(C) below. Example 3 demonstrated that acceptable quality pellets can be prepared using the method described herein with different pelletizing apparatuses when the order of addition of the gum and resin is used.

[0077] Using the pellets prepared according to the method of Example 1 with composition numbers 4 and 3 in Table 2 above, a silicone pressure-sensitive adhesive was produced.

[0078] Example 4 Additional pellets were prepared using the procedure of Example 1 with the starting materials shown in Table 3. Gum 4 was fed into the first port of the extruder, and either the resin or a blend of resin and gum was fed into the second port.

[0079]

Table 3

[0080] Example 5 An aqueous dispersion based on a silicone pressure-sensitive adhesive was prepared as follows. The pellets prepared as described in Example 4 were fed by a loss-in-weight screw feeder into the first barrel of a 25 mm twin-screw extruder (Coperion ZSK26, L / D = 48 and 12 steps), and subsequently, the gum was fed into the second or third barrel by a gear pump. The surfactant was injected into the fourth (or fifth or sixth) barrel by a piston pump (ISCO 1000D) together with 5 - 25% (weight ratio with respect to the silicone solid, i.e., the combination of the resin and the gum) water. The remaining water was injected into further downstream barrels (e.g., the eighth to twelfth). All barrels were set at 80 - 120 °C, and the extruder was operated at 300 - 900 RPM. The silicone pressure-sensitive adhesive-based aqueous dispersion was collected at the exit of the extruder.

[0081] The amounts of each starting material are shown below in Table 4.

[0082]

Table 4

[0083] Example 6 An aqueous dispersion of the silicone pressure-sensitive adhesive composition was prepared as follows.

[0084] 10 grams of the prepared dispersion, a specific weight of an initiator (PERKADOX™ L-40 RPS, Nouryon), and optionally some additives were added together directly and mixed at 2000 RPM for 1 minute by a SpeedMixer™.

[0085] The amounts of each starting material are shown below in Table 5.

[0086]

Table 5

[0087] Example 7 The sample prepared in Example 6 was tested for adhesion to SUS according to the following test method. The results are shown in Table 6.

[0088]

Table 6

[0089] The test method used in this specification included the following.

[0090] The particle size was measured by a Beckman Coulter LS230 Laser Diffraction Particle Size Analyzer.

[0091] The adhesion to stainless steel (SUS) was tested according to the following procedure. Using four bird bards, an aqueous dispersion of the silicone pressure-sensitive adhesive composition was drawn down onto two PET substrates. The coated substrates were heated at 80 °C for 2 minutes and at 180 °C for 3 minutes. Then, the coated substrates were cooled and cut into 1-inch wide strips. The 1-inch strips were applied to a clean stainless steel panel / glass. The samples were tested on a TMI peel and adhesion tester by pulling at 180 °C and 12 inches / minute the next day. The unit was grams / inch.

[0092] The weight average molecular weight and number average molecular weight of the starting materials containing the above gum and resin can be measured by gel permeation chromatography (GPC) according to the test method of Reference Example 1 starting from column 31 of US Patent No. 9,593,209. Industrial Applicability

[0093] The above examples show that a silicone pressure-sensitive adhesive having good adhesion to stainless steel can be prepared by the process described herein. Inventive Examples 7 and 8 show that additives can be included in the samples (comparable to Inventive Examples 2 and 3, respectively) and that these can improve adhesion. Definition and Use of Terms

[0094] Unless otherwise indicated by the context of this specification, all amounts, ratios, and percentages herein are by weight; the articles “a,” “an,” and “the” each refer to one or more; and the singular forms include the plural forms. The “Summary of the Invention” and “Abstract” are incorporated herein by reference. The transitional phrases “comprising,” “consisting essentially of,” and “consisting of” are used as described in Sections §2111.03 I., II., and III. of the Manual of Patent Examining Procedure Ninth Edition, Revision 08.2017, Last Revised January 2018. The use of “for example,” “e.g.,” “such as,” and “including” to list examples is not limited to the examples listed. Thus, “for example” or “such as” means “for example, but not limited to” or “such as, but not limited to” and includes other similar or equivalent examples. Materials of the DOWSIL (trademark), SILASTIC (trademark), and SYL-OFF (trademark) brands are commercially available from Dow Silicones Corporation (Midland, Michigan, USA). The abbreviations used herein have the definitions in Table 8.

[0095] [Table 7]

[0096] Embodiments of the present invention In the first embodiment, the process for preparing an aqueous dispersion based on a silicone pressure-sensitive adhesive from solvent-free polyorganosiloxane pellets is as follows: 1) An extruder comprising a barrel having a first feed port, a second feed port, and an outlet having a die, heating means configured to heat the barrel, and a screw mechanism housed within the barrel, wherein the first feed port and the second feed port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first feed port and the second feed port towards the outlet, the first feed port is upstream of the second feed port, and the second feed port is upstream of the outlet, providing an extruder. 2) i) Adding at least a portion of the solvent-free polydiorganosiloxane gum through the first feed port into the extruder; and ii) adding the solvent-free polyorganosilicate resin through the second feed port into the extruder, wherein the gum and the resin are added in amounts such that the weight ratio of resin:gum is from 2.1:1 to 5:1. 3) Mixing the solvent-free polydiorganosiloxane gum and the solvent-free polyorganosilicate resin within the barrel while heating the barrel at a temperature of 200°C to 250°C, thereby forming a mixture. 4) Transporting the mixture through the die of the outlet, thereby forming a strand. 5) Cooling the strand exiting the die. 6) Grinding the strand, thereby preparing solvent-free polyorganosiloxane pellets. 7) Supplying a starting material to the dispersion device, the starting material including the pellets prepared in step 6), a surfactant selected from the group consisting of an anionic surfactant, a nonionic surfactant, and a combination of both, water, and an optionally additional polydiorganosiloxane gum in an amount sufficient to adjust the resin:gum ratio to 0.4:1 to 3:1, provided that the surfactant does not include sulfonic acid and its salt derivatives, long-chain carboxylic acid surfactants and their salts, fatty acid amines and amides, and their salts and derivatives, alkyl glucosides, and linear silicone polyethers. 8) Mixing and heating the starting material from step 7) in the dispersion device, thereby producing an aqueous dispersion of the silicone pressure-sensitive adhesive base.

[0097] In the second embodiment, the process of the first embodiment further includes, before step 2), preparing a solvent-based polyorganosilicate resin and devolatilizing the solvent-based polyorganosilicate resin to form a solvent-free polyorganosilicate resin.

[0098] In the third embodiment, in the process of the first or second embodiment, the solvent-free polyorganosilicate resin includes the unit formula (R 1 R 2 2SiO 1 / 2 ) w (R 2 3SiO 1 / 2 ) x (SiO 4 / 2 ) y X z wherein each R 2 is independently selected from the group consisting of an alkyl group having 1 to 18 carbon atoms and an aryl group having 6 to 18 carbon atoms, each R 2 is an alkenyl group having 2 to 18 carbon atoms independently selected, X represents a hydrolyzable substituent, subscript w≧0, subscript x>4, subscript y>1, subscript z≧0, provided that the amount (w + x + y + z) is sufficient to give the resin a number average molecular weight of 2,000 g / mol to 15,000 g / mol.

[0099] In the fourth embodiment, in any one of the processes of the first to third embodiments, the solventless polydiorganosiloxane gum has a unit formula (R 3 R 2 2SiO 1 / 2 ) a (R 2 2SiO 2 / 2 ) b (R 2 SiO 3 / 2 ) c and in the formula, each R 2 is independently selected from the group consisting of alkyl groups having 1 to 18 carbon atoms and aryl groups having 6 to 18 carbon atoms, and each R 3 is a curable group, with subscript a ≥ 2, subscript b > 5000, and subscript c ≥ 0, provided that the amount (a + b + c) is sufficient to provide the gum having a number average molecular weight of 150,000 g / mol to 1,000,000 g / mol.

[0100] In the fifth embodiment, in any one of the processes of the first to fourth embodiments, all the gums are added to the first supply port.

[0101] In the sixth embodiment, in any one of the processes of the first to fifth embodiments, 0 to 15% of the gum is added to the second supply port.

[0102] In the seventh embodiment, in any one of the processes of the first to sixth embodiments, steps 5) and 6) are carried out using a water pelletizer.

[0103] In the eighth embodiment, in any one of the processes of the first to seventh embodiments, the dispersing device in step 7) is an additional extruder.

[0104] In the ninth embodiment, the process for preparing an aqueous dispersion of the silicone pressure-sensitive adhesive composition is 1) An extruder comprising a barrel having a first supply port, a second supply port, and an outlet having a die, heating means configured to heat the barrel, and a screw mechanism housed in the barrel, wherein the first supply port and the second supply port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first supply port and the second supply port toward the outlet, the first supply port is upstream of the second supply port, and the second supply port is upstream of the outlet, and providing the extruder. 2) i) Adding at least a part of a solvent-free polydiorganosiloxane gum through the first supply port to the extruder; and ii) adding a solvent-free polyorganosilicate resin through the second supply port to the extruder, wherein the gum and the resin are added in an amount such that the weight ratio of resin:gum is from 2.1:1 to 5:1. 3) Mixing the solvent-free polydiorganosiloxane gum and the solvent-free polyorganosilicate resin in the barrel while heating the barrel at a temperature of 200°C to 250°C to thereby form a mixture. 4) Transporting the mixture through the die of the outlet to thereby form a strand. 5) Cooling the strand exiting the die. 6) Crushing the strand to thereby prepare solvent-free polyorganosiloxane pellets. 7) Supplying to a dispersing device a starting material comprising the pellets prepared in step 6), a surfactant selected from the group consisting of anionic surfactants, ionic surfactants, and combinations thereof, water, and an optionally additional polydiorganosiloxane gum in an amount sufficient to adjust the resin:gum ratio to from 0.4:1 to 2:1, provided that the surfactant does not include sulfonic acids and their salt derivatives, long-chain carboxylic acid surfactants and their salts, fatty acid amines and amides, and their salts and derivatives, alkyl glucosides, and linear silicone polyethers. 8) Mixing and heating the starting material from step 7) in the dispersing device to thereby produce an aqueous dispersion of a silicone pressure-sensitive adhesive base. 9) Adding additional starting materials to an aqueous dispersion based on a silicone pressure-sensitive adhesive, wherein the additional starting materials are selected from the group consisting of free radical initiators, solvents, coating additives, and combinations thereof, and thereby forming an aqueous dispersion of a silicone pressure-sensitive adhesive composition.

[0105] In a tenth embodiment, in the process of the ninth embodiment, a coating additive is present, and the coating additive is selected from the group consisting of defoamers, wetting agents, and pH adjusting additives.

[0106] In an eleventh embodiment, a process for preparing an adhesive article includes the following. 11. 1) An extruder comprising a barrel having a first feed port, a second feed port, and an outlet having a die, heating means configured to heat the barrel, and a screw mechanism housed within the barrel, wherein the first feed port and the second feed port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first feed port and the second feed port towards the outlet, the first feed port is upstream of the second feed port, and the second feed port is upstream of the outlet, and providing the extruder. 2) i) Adding at least a portion of a solventless polydiorganosiloxane gum through the first feed port to the extruder; and ii) adding a solventless polyorganosilicate resin through the second feed port to the extruder, wherein the gum and the resin are added in amounts such that the weight ratio of resin:gum is from 2.1:1 to 5:1. 3) Mixing the solventless polydiorganosiloxane gum and the solventless polyorganosilicate resin within the barrel while heating the barrel at a temperature of 200°C to 250°C, thereby forming a mixture. 4) Transporting the mixture through the die of the outlet, thereby forming a strand. 5) Cooling the strand exiting the die. 6) grinding the strands, thereby preparing solvent-free polyorganosiloxane pellets; 7) feeding the pellets prepared in step 6) and starting materials including sulfonic acid and its salt derivatives, long chain carboxylic acid surfactants and their salts, quaternary ammonium salts, fatty acid amines and amides and their salts and derivatives, betaines, alkylglucosides, and linear silicone polyether-free surfactants, water, and optionally additional polydiorganosiloxane gum in an amount sufficient to adjust the resin:gum ratio to between 0.4:1 and 2:1 into a dispersing device; 8) mixing and heating the starting materials from step 7) in a dispersing device, thereby producing a silicone pressure sensitive adhesive-based water-based dispersion; 9) adding additional starting materials to the aqueous dispersion of the silicone pressure sensitive adhesive base, the additional starting materials being selected from the group consisting of free radical initiators, solvents, coating additives, and combinations thereof, thereby forming an aqueous dispersion of a silicone pressure sensitive adhesive composition; Optionally, 10) treating a surface of the substrate; and 11) coating an aqueous dispersion of a silicone pressure sensitive adhesive composition onto a surface of a substrate; Optionally, 12) removing all or a portion of the water, and, if present, the solvent, to form a layer of the pressure sensitive adhesive composition on the surface of the substrate; 13) curing the silicone pressure sensitive adhesive composition to form a silicone pressure sensitive adhesive.

Claims

1. A process for preparing an aqueous dispersion based on a silicone pressure-sensitive adhesive from solvent-free polyorganosiloxane pellets, said process comprising 1) An extruder comprising a barrel having a first feed port, a second feed port, and an outlet having a die, heating means configured to heat said barrel, and a screw mechanism housed within said barrel, wherein said first feed port and said second feed port are configured to introduce starting materials into said extruder, said screw mechanism being capable of mixing said starting materials and transporting them from said first feed port and said second feed port towards said outlet, said first feed port being upstream of said second feed port, and said second feed port being upstream of said outlet, providing an extruder; 2) i) adding at least a portion of a solvent-free polydiorganosiloxane gum through said first feed port into said extruder; and ii) adding a solvent-free polyorganosilicate resin through said second feed port into said extruder, said gum and said resin being added in amounts such that the weight ratio resin:gum is from 2.1:1 to 5:1; 3) mixing said solvent-free polydiorganosiloxane gum and said solvent-free polyorganosilicate resin within said barrel while heating said barrel at a temperature of from 200°C to 250°C, thereby forming a mixture; 4) transporting said mixture through said die of said outlet, thereby forming a strand; 5) cooling said strand before it exits said die; 6) grinding said strand, thereby preparing said solvent-free polyorganosiloxane pellets; 7) supplying to a dispersing device starting materials comprising the pellets prepared in step 6), an optionally additional amount of polydiorganosiloxane gum sufficient to adjust the resin:gum ratio to from 0.4:1 to 3:1, a surfactant selected from the group consisting of anionic surfactants, nonionic surfactants, and combinations thereof, and water, provided that said surfactant does not include sulfonic acids and their salt derivatives, long-chain carboxylic acid surfactants and their salts, fatty acid amines and amides, and their salts and derivatives, alkyl glucosides, and linear silicone polyethers; (8) Mixing and heating the starting material from step (7) in the dispersing device, thereby producing the aqueous dispersion of the silicone pressure-sensitive adhesive base, a process comprising.

2. Before step (2), further comprising preparing a solvent-based polyorganosilicate resin and devolatilizing the solvent-based polyorganosilicate resin to form the solvent-free polyorganosilicate resin, the process according to claim 1.

3. The solvent-free polyorganosilicate resin has the unit formula (R １ R ２ ２ SiO １／２ )(R ｗ R ２ ３ SiO １／２ )(SiO ｘ )(SiO ４／２ )(R ｙ X ｚ ), where each R ２ is independently selected from the group consisting of alkyl groups having 1 to 18 carbon atoms and aryl groups having 6 to 18 carbon atoms, each R １ is an alkenyl group having 2 to 18 carbon atoms selected independently, X represents a hydrolyzable substituent, subscript w≥0, subscript x>4, subscript y>1, subscript z≥0, provided that the amount (w + x + y + z) is sufficient to give the resin a number average molecular weight of 2,000 g / mol to 15,000 g / mol. The process according to claim 1.

4. The solventless polydiorganosiloxane gum has the unit formula (R ３ R ２ ２ SiO １／２ ), ａ (R ２ ２ SiO ２／２ ), ｂ (R ２ SiO ３／２ ), ｃ wherein each R ２ is independently selected from the group consisting of alkyl groups having 1 to 18 carbon atoms and aryl groups having 6 to 18 carbon atoms, each R ３ is a curable group, subscript a ≥ 2, subscript b > 5000, subscript c ≥ 0, provided that the amount (a + b + c) is sufficient to provide said gum having a number average molecular weight of 150,000 g / mol to 1,000,000 g / mol, the process according to claim 1.

5. The process according to claim 1, wherein all of the gum is added to the first supply port.

6. The process according to claim 1, wherein 0 to 15% of the gum is added to the second supply port.

7. The process according to claim 1, wherein steps (5) and (6) are carried out using a underwater pelletizer.

8. The process according to claim 1, wherein the dispersing device in step (7) is an additional extruder.

9. A process for preparing an aqueous dispersion of a silicone pressure-sensitive adhesive composition, the process comprising I) carrying out the process according to any one of claims 1 to 8 to form the aqueous dispersion of the silicone pressure-sensitive adhesive base; and II) adding additional starting materials to the aqueous dispersion of the silicone pressure-sensitive adhesive base, the additional starting materials being selected from the group consisting of free radical initiators, solvents, coating additives, and combinations thereof, thereby forming the aqueous dispersion of the silicone pressure-sensitive adhesive composition.

10. The process according to claim 9, wherein the coating additive is present and the coating additive is selected from the group consisting of defoamers, wetting agents, and pH adjusting additives.

11. A method for preparing an adhesive article, comprising optionally, 1) treating the surface of a substrate; 2) carrying out the process according to claim 9 to form the aqueous dispersion of the silicone pressure-sensitive adhesive composition and coating the surface of the substrate with the aqueous dispersion of the silicone pressure-sensitive adhesive composition; optionally, 3) removing all or part of the water and, if present, the solvent to form a layer of the pressure-sensitive adhesive composition on the surface of the substrate; and 4) curing the silicone pressure-sensitive adhesive composition to form a silicone pressure-sensitive adhesive.

12. A process for preparing solventless polyorganosiloxane pellets, 1) An extruder comprising a barrel having a first feed port, a second feed port, and an outlet having a die, heating means configured to heat the barrel, and a screw mechanism housed within the barrel, wherein the first feed port and the second feed port are configured to introduce starting materials into the extruder, the screw mechanism is capable of mixing the starting materials and transporting them from the first feed port and the second feed port towards the outlet, the first feed port is upstream of the second feed port, and the second feed port is upstream of the outlet, providing an extruder; 2) i) adding at least a portion of the solventless polydiorganosiloxane gum through the first feed port into the extruder; and ii) adding a solventless polyorganosilicate resin through the second feed port into the extruder, wherein the gum and the resin are added in amounts such that the weight ratio of resin:gum is from 2.1:1 to 5:1; 3) mixing the solventless polydiorganosiloxane gum and the solventless polyorganosilicate resin within the barrel while heating the barrel at a temperature of 200°C to 250°C, thereby forming a mixture; 4) transporting the mixture through the die at the outlet, thereby forming a strand; 5) cooling the strand exiting the die; 6) grinding the strand, thereby preparing the solventless polyorganosiloxane pellets, the process comprising.

13. The solvent-free polyorganosilicate resin has the unit formula (R １ R ２ ２ SiO １／２ ), ｗ (R ２ 3SiO １／２ ), ｘ (SiO ４／２ ), ｙ X ｚ and in the formula, each R ２ is independently selected from the group consisting of alkyl groups having 1 to 18 carbon atoms and aryl groups having 6 to 18 carbon atoms, each R １ is an alkenyl group having 2 to 18 carbon atoms independently selected, X represents a hydrolyzable substituent, subscript w≥0, subscript x>4, subscript y>1, subscript z≥0, provided that the amount (w + x + y + z) is sufficient to give the resin a number average molecular weight of 2,000 g / mol to 15,000 g / mol. The process according to claim 12.

14. wherein the solventless polydiorganosiloxane gum has the unit formula (R ３ R ２ ２ SiO １／２ ), ａ (R ２ ２ SiO ２／２ ), ｂ (R ２ SiO ３／２ ), ｃ and wherein each R ２ is independently selected from the group consisting of alkyl groups having 1 to 18 carbon atoms and aryl groups having 6 to 18 carbon atoms, and each R ３ is a curable group, with subscript a ≥ 2, subscript b > 5000, and subscript c ≥ 0, provided that the amount (a + b + c) is sufficient to provide the gum having a number average molecular weight of 150,000 g / mol to 1,000,000 g / mol, the process according to claim 12.

15. The process according to claim 14, wherein the weight ratio of resin:gum is from 2.1:1 to 3.5:1.

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