阅读说明：本技术 耐酸粘合剂组合物 (Acid resistant adhesive composition ) 是由 张新玉 陈其 于 2017-12-29 设计创作，主要内容包括：本发明涉及一种耐酸粘合剂组合物,其包含：至少一种聚氯丁二烯、至少一种环氧硅烷、至少一种胺硅烷、至少一种不饱和硅烷、以及至少一种有机溶剂；所述耐酸粘合剂组合物在被浸入电解质溶液中后表现出优异的初始剥离强度和最终剥离强度,并且显示出良好的耐酸性能。(The present invention relates to an acid resistant adhesive composition comprising: at least one polychloroprene, at least one epoxy silane, at least one amine silane, at least one unsaturated silane, and at least one organic solvent; the acid-resistant adhesive composition exhibits excellent initial peel strength and final peel strength after being immersed in an electrolyte solution, and exhibits good acid resistance.)

1. An acid resistant adhesive composition comprising:

(a) at least one polychloroprene rubber;

(b) at least one epoxy silane;

(c) at least one aminosilane;

(d) at least one unsaturated silane; and

(e) at least one organic solvent.

2. The acid resistant adhesive composition of claim 1 wherein the epoxy silane is an epoxidized alkoxysilane, preferably selected from the group consisting of glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, β - (3, 4-epoxycyclohexyl) -ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and any combination thereof.

3. The acid resistant adhesive composition of claim 1 or 2 wherein the epoxy silane is present in an amount of from 0.2 to 1 weight percent, preferably from 0.4 to 0.6 weight percent, based on the total weight of the composition.

4. The acid resistant binder composition according to any of the preceding claims, wherein the aminosilane is an alkoxysilane containing amine, preferably selected from the group consisting of gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropyltriisopropoxysilane, gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, gamma- (2-aminoethyl) aminopropyltrimethoxysilane, gamma- (6-aminohexyl) aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, gamma-aminopropyl-triisopropoxysilane, gamma-aminopropylmethyldimethoxysilane, gamma-aminopropyl-trimethoxysilane, gamma-aminopropyl, 4-amino-3, 3-dimethylbutyltrimethoxysilane, 4-amino-3, 3-dimethylbutyldimethoxymethylsilane, 3- (N-ethylamino) -2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyldiethoxymethylsilane, N-ethyl-3-amino-2-methylpropyltriethoxysilane, N-ethyl-3-amino-2-methylpropylmethyldimethoxysilane, N-butyl-3-amino-2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyltrimethoxysilane, N-methyl-3-amino-2-methylpropyltrimethoxysilane, N-phenyl-gamma-aminopropyltrimethoxysilane, N-benzyl-gamma-aminopropyltrimethoxysilane, N-vinylbenzyl-gamma-aminopropyltriethoxysilane, and any combination thereof.

5. The acid resistant adhesive composition of any one of the preceding claims wherein the aminosilane is present in an amount of 0.2 to 2 weight percent, preferably 0.4 to 1 weight percent, based on the total weight of the composition.

6. The acid resistant adhesive composition of any of the preceding claims wherein the unsaturated silane is an ethylenically unsaturated alkoxysilane, preferably selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and any combination thereof.

7. The acid resistant adhesive composition of any one of the preceding claims wherein the unsaturated silane is present in an amount of from 0.2 to 2 weight percent, preferably from 0.4 to 1 weight percent, based on the total weight of the composition.

8. The acid resistant adhesive composition of any one of the preceding claims further comprising at least one stabilizer, preferably selected from the group consisting of acrylic modified halogenated polyolefins, methacrylic modified halogenated polyolefins, and any combination thereof.

9. The acid resistant adhesive composition of any one of the preceding claims further comprising at least one saturated silane, preferably selected from the group consisting of saturated alkoxysilanes, saturated alkylsilanes, and any combination thereof.

10. The acid resistant adhesive composition of any one of the preceding claims further comprising at least one film forming agent, preferably selected from the group consisting of styrene-butadiene-styrene (SBS) block copolymers and styrene-isoprene-styrene (SIS) block copolymers, styrene-ethylene-butylene-styrene (SEBS) block copolymers, styrene-ethylene-propylene-styrene (SEPS) block copolymers, ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), and any combination thereof.

11. The acid resistant adhesive composition of any one of the preceding claims further comprising at least one adhesion promoter, and at least one metal oxide.

12. The acid resistant adhesive composition of any one of the preceding claims comprising:

(a)8 to 25 weight percent of at least one polychloroprene rubber;

(b)0.2 to 1% by weight of at least one epoxy silane;

(c)0.2 to 2 wt% of at least one aminosilane;

(d)0.2 to 2 wt% of at least one unsaturated silane;

(e)1 to 5% by weight of at least one stabilizer;

(f)4 to 10 wt% of at least one tackifier;

(g)0.3 to 10 wt% of at least one adhesion promoter;

(h)20 to 80 wt% of at least one organic solvent;

(i)0.2 to 3% by weight of at least one saturated silane;

(j)0.3 to 2 wt% of at least one film former; and

(k)0.2 to 4% by weight of at least one metal oxide;

wherein the weight percentages of all components add up to 100 weight%.

13. A method of making the acid resistant adhesive composition of any of the preceding claims comprising the steps of:

(a) grinding the polychloroprene rubber;

(b) heating the ground polychloroprene rubber together with an optionally added metal oxide and forming a sheet of polychloroprene rubber by roll milling;

(c) mixing an organic solvent, an unsaturated silane, and optionally an added saturated silane to form a homogeneous mixture;

(d) dissolving the polychloroprene rubber sheet from step (b) in the homogeneous mixture from step (c) to form a solution;

(e) optionally adding a tackifier, an adhesion promoter, a film former and a stabilizer to the solution;

(f) mixing an epoxy silane and an amine silane; and

(g) adding a mixture of an epoxy silane and an amine silane to the solution from step (d) or step (e);

wherein steps (a) to (g) are all protected with nitrogen.

14. An article bonded by the acid resistant adhesive composition according to any one of claims 1 to 12.

15. A battery comprising the article of claim 14.

Technical Field

The present invention relates to an acid resistant adhesive composition comprising: at least one polychloroprene; at least one epoxy silane; at least one amine silane; at least one unsaturated silane; and at least one organic solvent. The acid-resistant adhesive composition according to the present invention exhibits excellent initial and final peel strengths after being immersed in an electrolyte solution, and exhibits good acid resistance.

Background

Lithium ion batteries have been widely used as rechargeable batteries in portable terminal devices (e.g., mobile phones, notebook computers, video cameras, etc.) because of their high energy output in spite of their extremely thin shape and compact size.

One of the limiting factors in the development of lithium ion batteries is the packaging material used to house the positive electrode, negative electrode, separator (separator) and electrolyte solution of the lithium ion battery, the electrolyte solution in lithium ion batteries typically contains a lithium salt that acts as an electrolyte, such as L iPF6 and L ibbf 4 in the presence of water, the lithium salt will be hydrolyzed to form hydrofluoric acid (HF), causing corrosion to the metal surface.

However, polymeric materials generally have a small polarizability and are extremely difficult to adhere. In order to adhere the polymer layer to the metal layer, it is often necessary to first treat the surface of the polymer layer. Chromate conversion has proven to be one of the most effective methods for achieving this. Graft modification is also used to improve the adhesive strength between the polymer layer and the metal layer. The polymer layer grafted with the polar monomer may have a higher surface polarity, which will improve the adhesive strength between the polymer layer and the metal layer.

Although great progress has been made in the development of attaching polymer layers to metal layers, the peel strength between the two layers has not been high enough to meet the requirements for packaging materials for lithium ion batteries. Furthermore, the process for treating the surface of the polymer layer is also complex and costly. Therefore, it is required to develop an acid-resistant adhesive composition for improving adhesion between a polymer layer and a metal layer and protecting the metal layer from corrosion of an electrolyte solution.

Disclosure of Invention

The present invention relates to an acid resistant adhesive composition comprising:

(a) at least one polychloroprene rubber;

(b) at least one epoxy silane;

(c) at least one aminosilane;

(d) at least one unsaturated silane; and

(e) at least one organic solvent.

The acid-resistant adhesive composition of the present invention exhibits excellent initial peel strength and final peel strength after being immersed in an electrolyte solution. Furthermore, the final peel strength of the acid resistant adhesive composition did not decrease much compared to the initial peel strength, indicating that the adhesive composition has good acid resistance.

The invention also relates to a method for preparing the acid-resistant adhesive composition, which is implemented under the protection of nitrogen and comprises the following steps:

(a) grinding the polychloroprene rubber;

(b) heating the ground polychloroprene rubber together with an optionally added metal oxide and forming a sheet of polychloroprene rubber by roll milling;

(c) mixing an organic solvent, an unsaturated silane, and optionally an added saturated silane to form a homogeneous mixture;

(d) dissolving the polychloroprene rubber sheet from step (b) in the homogeneous mixture from step (c) to form a solution;

(e) optionally adding a tackifier, an adhesion promoter, a film former and a stabilizer to the solution;

(f) mixing an epoxy silane and an amine silane; and

(g) adding a mixture of an epoxy silane and an amine silane to the solution from step (d) or step (e).

The invention also relates to an article bonded by the acid resistant adhesive composition.

The invention also relates to a battery comprising the article.

The invention also relates to a portable device or an electric vehicle comprising the battery.

Detailed Description

In the following paragraphs, the present invention will be described in more detail. Each aspect so described may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In the context of the present invention, the terms used are to be interpreted according to the following definitions, unless the context dictates otherwise.

As used herein, the singular forms "a", "an", "the" and "the" include both singular and plural referents unless the context clearly dictates otherwise.

As used herein, the term "comprising" is synonymous with "including" or "containing," is inclusive or open-ended, and does not exclude additional unrecited members, elements, or method steps.

The recitation of numerical endpoints includes all numbers and fractions subsumed within the corresponding range, as well as the recited endpoints.

All references cited in this specification are incorporated herein by reference in their entirety.

Unless defined otherwise, all terms (including technical and scientific terms) used in disclosing the invention have the meaning commonly understood by one of ordinary skill in the art to which this invention belongs. By way of further guidance, definitions of terms are included to better understand the teachings of the present invention.

Polychloroprene rubber

The polychloroprene rubber of the present invention means a chloroprene homopolymer and a copolymer of chloroprene and another monomer copolymerizable with chloroprene. Other monomers copolymerizable with chloroprene for use in the present invention include, but are not limited to: acrylic esters such as methyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; methacrylates such as methyl methacrylate, butyl methacrylate and 2-ethylhexyl methacrylate; 2, 3-dichloro-1, 3-butadiene, 1-chloro-1, 3-butadiene, isoprene, ethylene, styrene, acrylonitrile, and derivatives thereof.

Examples of commercially available polychloroprene rubbers are: for example, Neoprene WHV and Neoprene W from DuPont; skprene G-40S-1, Skpyrene Y-30S and Skpyrene 580H from TOSOH Corporation.

In some embodiments of the invention, the amount of polychloroprene rubber in the acid resistant adhesive composition of the present invention is from 5 to 20 weight percent, preferably from 10 to 15 weight percent, based on the total weight of the composition.

Epoxy silane

The epoxy silane of the present invention acts as a coupling agent. In some embodiments, the epoxy silane comprises at least one epoxidized alkoxysilane comprising at least one epoxy group and at least one alkoxy group attached to a silicon atom.

Examples of epoxy silanes are glycidoxypropyltrimethoxysilane, glycidoxypropyltriethoxysilane, β - (3, 4-epoxycyclohexyl) -ethyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, and any combination thereof.

Examples of commercially available epoxy silanes are, for example, KMB 403 from Shin-Etsu Chemical, SI L QUEST A187 from Momentive, and Dynasylan G L YMO from Evonic Industries AG.

In some embodiments of the invention, the amount of epoxy silane of the present invention is from 0.2 to 1 weight percent, preferably from 0.4 to 0.6 weight percent, based on the total weight of the composition.

Amino silane

The aminosilanes of the present invention act as coupling agents. In some embodiments, the aminosilane comprises at least one alkoxysilane-containing amine (amine stabilizing alkoxy silane) comprising at least one amino group and at least one alkoxy group attached to a silicon atom.

Examples of aminosilanes include, but are not limited to: gamma-aminopropyltrimethoxysilane, gamma-aminopropyltriethoxysilane, gamma-aminopropyltriisopropoxysilane, gamma-aminopropylmethyldimethoxysilane, gamma-aminopropylmethyldiethoxysilane, gamma- (2-aminoethyl) aminopropyltrimethoxysilane, gamma- (6-aminohexyl) aminopropyltrimethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 4-amino-3, 3-dimethylbutyltrimethoxysilane, 4-amino-3, 3-dimethylbutylmethoxysilane, gamma-aminopropyl-trimethoxysilane, gamma-aminopropyl-methyldimethoxysilane, gamma-aminopropyl-methyldiethoxysilane, gamma-aminopropyl-trimethoxysilane, gamma-aminopropyl-methyldimethoxysilane, gamma-3-aminopropyl, 3- (N-ethylamino) -2-methylpropyltrimethoxysilane, N-ethyl-3-amino-2-methylpropyldiethoxymethylsilane, N-ethyl-3-amino-2-methylpropyltriethoxysilane, N-ethyl-3-amino-2-methylpropylmethyldimethoxysilane, n-butyl-3-amino-2-methylpropyltrimethoxysilane, N-phenyl-gamma-aminopropyltrimethoxysilane, N-benzyl-gamma-aminopropyltrimethoxysilane, N-vinylbenzyl-gamma-aminopropyltriethoxysilane, and any combination thereof. Specific examples of aminosilanes are shown below.

Examples of commercially available aminosilanes are, for example, KMB 603 from Shin-Etsu Chemical, SI L QUEST A1120 from Momentive, and GENIOSI L GF9 from Wacker Chemie AG.

In some embodiments of the invention, the amount of aminosilane is 0.2 to 2 wt.%, preferably 0.4 to 1 wt.%, based on the total weight of the composition.

Unsaturated silanes

Unsaturated silane of the present invention refers to any conventional silane containing one or more non-aromatic carbon-carbon double bonds. The unsaturated silane acts as a coupling agent and is preferably an ethylenically unsaturated alkoxysilane selected from the group consisting of vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, and any combination thereof.

Commercially available unsaturated silanes are for example KMB 1003 from Shin-Etsu Chemical, SI L QUEST A171 from Momentive, and Dynasylan VTMO from Evonic Industries AG.

In some embodiments of the invention, the amount of unsaturated silane is from 0.2 to 2 weight percent, preferably from 0.4 to 1 weight percent, based on the total weight of the composition.

Organic solvent

The organic solvent of the present invention means any general organic solvent, and may be selected from aromatic solvents, ketone compounds, aliphatic solvents, alicyclic solvents, ester solvents, chlorinated hydrocarbon compounds, and any combination thereof.

In some embodiments of the present invention, the organic solvent may be selected from the group consisting of toluene, xylene, acetone, methyl ethyl ketone, hexane, cyclohexane, methylcyclohexane, ethyl acetate, butyl acetate, dichloromethane, and any combination thereof.

Examples of commercially available organic solvents include: MCH, EA and CH from SK Chemicals.

In some embodiments of the present invention, the amount of organic solvent is from 20 to 80 weight percent, preferably from 50 to 75 weight percent, based on the total weight of the composition.

Other optional additives

Tackifier

The tackifier of the present invention refers to any conventional tackifier, including but not limited to: aliphatic petroleum resins, cyclic petroleum resins, aromatic petroleum resins, gum resins, rosin resins, synthetic terpene resins, natural terpene resins, and any combination thereof.

Examples of commercially available tackifiers are, for example, Tamanol 803L from Arakawa Chemical, C100R, C100W, H130R and H130W from Eastman, H5-1000 and H5-1001 from the Chinese constant river, SU90, SU100, SU120 and SU130 from Kolonindustries, I-Marv P90, I-Marv P100 and I-Marv P120 from Idemitsu, Regalite R1100, Regalite R1120 and Regalite S1100 from Eastman, JH-6100 and JH-6125 from Jinhai Cheng Chenghai Chengguang.

In some embodiments of the invention, the amount of tackifier is from 4 to 10 wt%, preferably from 5 to 7 wt%, based on the total weight of the composition.

Adhesion promoter

The adhesion promoter of the present invention refers to any conventional adhesion promoter, preferably modified polyolefins, more preferably chlorinated polyolefins and acrylic (acrylic) modified polyolefins.

In some embodiments of the present invention, the adhesion promoter may be selected from the group consisting of chlorinated polypropylene, acrylic modified polypropylene, and any combination thereof.

Examples of commercially available adhesion promoters are, for example, Hardren DX-526P from Toyobo Co., L td. and AUROREN 550S from Nippon Paper Industries Co., L td..

In some embodiments of the invention, the amount of adhesion promoter is from 0.3 to 10 wt%, preferably from 0.5 to 6 wt%, based on the total weight of the composition.

Stabilizer

The stabilizer of the present invention refers to an acrylic-modified halogenated polyolefin or a methacrylic (methacrylic) -modified halogenated polyolefin or any combination thereof.

In some embodiments, the stabilizer may be selected from the group consisting of acrylic modified chlorinated polyethylene, acrylic modified chlorinated polypropylene, acrylic modified chlorinated polybutene, and any combination thereof.

Commercially available stabilizers are for example: XM 200 from chang pont chemical ltd, usa.

In some embodiments of the invention, the amount of stabilizer is 1 to 5 wt%, preferably 2 to 5 wt%, based on the total weight of the composition.

Saturated silanes

Without wishing to be bound by any theory, the saturated silanes of the present invention may function to absorb water that may be present in the acid resistant adhesive composition and prevent the epoxy, amino and unsaturated silanes from reacting with the water. In some embodiments, the saturated silane is a saturated alkoxysilane, a saturated alkylsilane, or a combination thereof.

Examples of saturated silanes include, but are not limited to: tetraethoxysilane, triethoxysilane, tetrapropoxysilane, tripropoxysilane, and any combination thereof.

Commercially available saturated silanes are, for example, tetraethyl orthosilicate (tetreatethyl ortho silicate) from singaponia chemical ltd.

In some embodiments of the invention, the amount of saturated silane is from 0.2 to 3 weight percent, preferably from 0.5 to 1 weight percent, based on the total weight of the composition.

Metal oxides

The metal oxide of the present invention means any general metal oxide which functions to improve curing of polychloroprene and to improve heat resistance of an acid-resistant adhesive. Preferably, the metal oxide is selected from the group consisting of magnesium oxide, zinc oxide, and combinations thereof. More preferably, the magnesium oxide is activated magnesium oxide and the zinc oxide is activated zinc oxide.

Commercially available metal oxides are for example Kyowamag 150 from Kyowa Chemical Industry Co., L td. and AZO from Seido Chemical Industry Co., L td..

In some embodiments of the invention, the amount of metal oxide is from 0.2 to 4 wt%, preferably from 0.4 to 3 wt%, based on the total weight of the composition.

Film forming agent

Film formers of the present invention include, but are not limited to: styrene-butadiene-styrene (SBS) block copolymers and styrene-isoprene-styrene (SIS) block copolymers, styrene-ethylene-butylene-styrene (SEBS) block copolymers, styrene-ethylene-propylene-styrene (SEPS) block copolymers, ethylene propylene rubber (EPM), ethylene propylene diene rubber (EPDM), and ethylene propylene diene rubber (ethylene propylene diene monomer) and any combinations thereof.

Commercially available film formers are, for example, Kraton D1102J and MD 1648 from Kraton.

In some embodiments of the present invention, the amount of film former is from 0.3 to 2 weight percent, preferably from 0.5 to 1 weight percent, based on the total weight of the composition.

In a preferred embodiment, the acid resistant adhesive composition comprises:

(a)8 to 25 weight percent of at least one polychloroprene rubber;

(b)0.2 to 1% by weight of at least one epoxy silane;

(c)0.2 to 2 wt% of at least one aminosilane;

(d)0.2 to 2 wt% of at least one unsaturated silane;

(e)1 to 5% by weight of at least one stabilizer;

(f)4 to 10 wt% of at least one tackifier;

(g)0.3 to 10 wt% of at least one adhesion promoter;

(h)20 to 80 wt% of at least one organic solvent;

(i)0.2 to 3% by weight of at least one saturated silane;

(j)0.3 to 2 wt% of at least one film former; and

(k)0.2 to 4% by weight of at least one metal oxide;

wherein the weight percentages of all components add up to 100 weight%.

The acid resistant adhesive composition can be prepared by the following steps under nitrogen protection:

a) grinding the polychloroprene rubber;

b) heating the ground polychloroprene rubber together with an optionally added metal oxide at a desired temperature of less than or equal to 85 ℃ and forming a polychloroprene rubber sheet by roll milling;

c) mixing an organic solvent, an unsaturated silane, and optionally an added saturated silane to form a homogeneous mixture;

d) dissolving the polychloroprene rubber sheet from step b) in the homogeneous mixture from step c) to form a solution;

e) optionally adding a tackifier, an adhesion promoter, a film former and a stabilizer to the solution and stirring the solution at a desired temperature (e.g., a temperature in the range of 25 ℃ to 40 ℃);

f) mixing an epoxy silane and an amine silane; and

g) adding a mixture of epoxy silane and amine silane to the solution from step d) or step e).

The initial peel strength of the acid resistant adhesive of the present invention can be evaluated by the following steps:

a) forming a laminate by bonding an untreated polymer and a metal with an acid resistant adhesive;

b) heating the laminate to cure the acid resistant adhesive;

c) peeling the untreated polymer and metal from each other at an angle of 180 °; and

d) when the untreated polymer and metal were pulled apart a predetermined distance, the force was recorded as the initial peel strength of the acid resistant adhesive.

The final peel strength of the acid resistant adhesive of the present invention can be evaluated by the following steps:

a) forming a laminate by bonding an untreated polymer and a metal with an acid resistant adhesive;

b) heating the laminate to cure the acid resistant adhesive;

c) immersing the laminate in an electrolyte solution;

d) removing the laminate from the electrolyte solution and storing the laminate at 25 ℃ and 55% relative humidity;

e) peeling the untreated polymer and metal from each other at an angle of 180 °; and

f) when the untreated polymer and metal were pulled apart a predetermined distance, the force was recorded as the final peel strength of the acid resistant adhesive.

The storability of the acid-resistant binder of the present invention can be evaluated by the following steps:

a) storing the acid-resistant adhesive in a sealed container with nitrogen protection;

b) removing the acid resistant adhesive from the sealed container and measuring an initial peel strength and a final peel strength of the acid resistant adhesive; and

c) evaluating the storability of the acid-resistant adhesive as "acceptable" if the final peel strength is greater than or equal to a predetermined percentage of the initial peel strength; the storability of the acid resistant adhesive is rated as "off-spec" if the final peel strength is less than a predetermined percentage of the initial peel strength.

The acid resistant adhesive composition of the present invention has excellent initial peel strength for bonding untreated polymers and metals. Further, the final peel strength of the acid resistant adhesive composition did not decrease much compared to the initial peel strength after the bonded polymer and metal were immersed in the electrolyte solution, indicating that the adhesive composition has good acid resistance. In a further embodiment, the acid resistant adhesive composition also has good storability after 6 months of storage in a sealed container at 5 ℃ to 15 ℃ with nitrogen protection.