Pressure-sensitive adhesives

Claim 2

A pressure-sensitive adhesive composition characterized by comprising: (a) a block copolymer represented by the general formula I(BAT) n wherein I represents the free radical initiator portion of an iniferter of the formula I(T) n ; T represents the termination portion of said iniferter; n is an integer of at least 2; B represents an elastic acrylic polymer block having a glass transition temperature of less than 0°C; and A represents a normally thermoplastic polymer block having a glass transition temperature of at least 30°C wherein said A-block is formed of a monomer selected from the group consisting of methyl methacrylate, polystyrylethyl methacrylate macromer, methyl methacrylate macromer, acrylic acid, acrylonitrile, isobornyl methacrylate, N-vinyl pyrrolidone, and mixtures thereof, the weight ratio of said B-block to said A-block in said block copolymer being from about 95:5 to 50:50; and (b) 0 to 150 parts by weight tackifier per 100 parts block copolymer.

Claim 3

The pressure-sensitive adhesive composition of claim 1 further characterized by said elastic acrylic polymer block being formed of a monomer comprising from about 75 to 100 percent by weight of at least one monomeric acrylic or methacrylic acid ester of a non-tertiary alcohol, said alcohol having from 1 to 14 carbon atoms with the average number of carbon atoms being about 4 to 12, and from zero to about 40 parts by weight of at least one polar monomer copolymerizable with said monomeric acrylic or methacrylic acid ester.

Claim 4

The pressure sensitive adhesive composition of claim 2 further characterized by the selection of such monomeric acrylic or methacrylic acid ester from the group consisting of isooctyl acrylate, 2-ethylhexyl acrylate, 2-methylbutyl acrylate, and butyl acrylate and the selection of said polar monomer from the group consisting of acrylic acid, methacrylic acid, itaconic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, N-vinyl pyrrolidone, and polyethylene oxide acrylate.

Claim 5

The pressure sensitive adhesive composition of claim 1 further characterized by the representation of said block copolymer by the formula wherein R₁, R₂, R₃ and R₄ are aliphatic or aromatic moieties which can be the same or different and which do not prevent the ability of I to promote free radical polymerization or with T to recombine with I or a polymer free radical segment including I; Y is a linking group having a functionality of x+y which does not substantially interfere with the ability of I to promote free radical polymerization or the ability of T to recombine with I or a polymer free radical segment including I; and x and y are each integers of at least 1 and the sum of x+y is not more than 12.

Claim 6

The pressure sensitive adhesive composition of claim 1 further characterized by the selection of said iniferter from the group consisting of xylylene bis (N,N-diethyl dithiocarbamate) and xylylene bis (N-carbazolyl dithiocarbamate).

Claim 7

An adhesive coated sheet material further characterized by comprising a backing at least partially coated over at least one major surface with the pressure-sensitive adhesive composition of claim 1.

Claim 8

The adhesive coated sheet of claim 6 further characterized by its ability to transport moisture therethrough.

Claim 9

The adhesive coated sheet material of claim 6 further characterized by having an MVT of at least 1000 grams per square meter per 24 hours.

Claim 10

The adhesive coated sheet material of claim 6 further characterized by having a T₀ of at least 0.50 N/100 and a T₄₈ of at least 0.40 N/100 mm.

Claim 11

A method of making the pressure-sensitive adhesive composition of claim 1 characterized by comprising: (a) mixing (1) an iniferter represented by the general formula I(T) n capable upon being subjected to an appropriate energy source of forming free radicals I(·) n and nT· wherein n is an integer of at least 2, I· is a highly reactive free radical capable of initiating free radical polymerization, and T· is a less reactive free radical which is generally much less capable of initiating free radical polymerization than I· but will rejoin with I(·) n or a free radical polymer segment free radically polymerized with I(·) n upon termination of said energy source and (2) a first monomer charge comprising acrylic monomer which is free radically polymerizable in the presence of I(·) n to form an acrylic polymer block having a glass transition temperature of less than 0°C; (b) exposing the mixture of (a) to an energy source capable of forming free radicals I(·) n and nT·; (c) maintaining the exposure of (b) until said first monomer charge polymerizes with I(·) n to form a free radical polymer segment represented by the formula I(B·) n wherein B represents an elastic acrylic polymer block having a glass transition temperature of less than 0°C formed of said first monomer charge; (d) terminating said exposure whereby to cause I(B·) n and nT· to combine to form a polymer represented by the formula I(BT) n ; (e) mixing I(BT) n with a second monomer charge comprising monomer which is free radically polymerizable in the presence of I(B·) n to a thermoplastic block having a glass transition temperature of at least 30°C; (f) exposing I(BT) n to an energy source capable of forming free radicals I(B·) n and nT·; (g) maintaining the exposure of (f) until said second monomer charge polymerizes with I(B·) n to form a free radical block copolymer segment represented by the formula I(BA·) n wherein A represents a normally thermoplastic polymer block having a glass transition temperature of at least 30°C formed of said second monomer charge wherein said A-block is formed of said second monomer selected from the group consisting of methyl methacrylate, polystyrylethyl methacrylate macromer, methyl methacrylate macromer, acrylic acid, acrylonitrile, isobornyl methacrylate, N-vinyl pyrrolidone, and mixtures thereof; (h) terminating the exposure of (f) whereby I(BA·) n and nT· combine to form a block copolymer represented by the formula I(BAT) n ; and (i) blending a compatible tackifier with said block copolymer at the ratio of from 0 to 150 parts by weight tackifier per 100 parts by weight of said copolymer.