Acidified polyamidoamine adhesives, method of manufacture, and use for creping and ply bond applications

Abstract

A paper adhesive composition includes a cationic non-crosslinked acidified solution of a polyamidoamine with the repeating unitswherein n≧1; m=1 or 2; X−m is chloride, bromide, iodide, sulfate, bisulfate, nitrate, oxalate, alkyl carboxylate, aryl carboxylate, hydrogen phosphate, dihydrogen phosphate, alkyl sulfonate, aryl sulfonate, or a combination comprising at least one of the foregoing anions; R1 is a divalent aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24 carbon atoms; R2 is hydrogen or a monovalent aliphatic, cycloaliphatic, or araliphatic group having from 1 to 24 carbon atoms; and R3 is a divalent hydrocarbon radical derived from a dibasic carboxylic acid.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This patent application claims the benefit of U.S. Provisional Patent Application Ser. No. 60 / 912,225 filed Apr. 17, 2007, the contents of which are hereby incorporated by reference in their entirety.BACKGROUND[0002]This disclosure relates to acidified polyamidoamine adhesive compositions, methods for their manufacture, and their use in creping and ply bonding applications.[0003]In the manufacture of certain wet-laid paper products, such as facial tissue, bathroom tissue, napkins, or paper towels, the web is conventionally subjected to a creping process in order to give it desirable textural characteristics, such as softness stretch and bulk. The creping process involves adhering the web to a rotating creping cylinder, such as a Yankee dryer, and then dislodging the adhered web with a doctor blade. The impact of the web against the doctor blade ruptures some of the fiber-to-fiber bonds within the web and causes the web to wrinkle or pucke...

AI Technical Summary

Benefits of technology

[0022]It has been discovered by the inventor hereof that acidified polyamidoamines in various embodiments are excellent creping and ply bond adhesives, used alone or in combination with epi-polyamides or when crosslinked with multivalent metal ions. Compositions are easily optimized for a range of adhesive properties.

Problems solved by technology

Greater adhesion increases softness, although generally with some loss of strength.

Both materials are non-crosslinked and provide high adhesion, and are considered highly moisture sensitive.

Disadvantages of these adhesives are that they dissolve easily (slight to no insolubility); they tend to associate with the sheet and the moisture in the sheet because they are not crosslinked; they have an uneven dryer coating profile; they have fair to poor Yankee dryer and blade protection (low add-on due to high adhesion); and some are corrosive, including PVOH.

As the pH is increased the product crosslinks, viscosity significantly increases and the product can become unstable, resulting in gellation.

They tend to build up on the dryer surface, which pushes the blade back and causes sheet picking.

They are ineffective on virgin fiber grades (low sheet moisture) that require high adhesion and better rewet.

They also accumulate on dryer edges (the hottest section of the dryer), causing uneven profile and / or sheet breaks.

The use of a bevel blade on bath tissue grades, however, can also have negative effects (such as lower bulk, bare spots on the dryer and excessive blade and dryer wear.

Limitations also arise in connection with use of the Yankee dryer crepe spray boom configuration.

Sometimes, debunizers (steam box prior to the vacuum pressure roll) or infrared heater are used for additional sheet drying and can affect the coating drying rate.

In most processes, there is no available space to move the spray boom closer to the blade holder to improve the adhesive's setting time.

Second, the spray boom dilution water rewets the existing coating base that remained on the dryer.

There are occasions when a heavily crosslinked adhesive can not be sufficiently rewetted and softened and the Z directional coating thickness builds up causing operational problems.

Other drawbacks are associated with water-soluble, thermosetting cationic epi-polyamide resins.

It is very difficult to vary these properties for a given creping machine.

With the water-soluble, thermosetting cationic epi-polyamide resins of the prior art, that degree of control has been difficult to achieve because the cross-linking of the adhesive occurs during the manufacturing process and it is impractical to have a number of water-soluble, thermosetting cationic epi-polyamide resins with different degrees of cross-linking in an attempt to tailor the creping adhesive to the creping process.

Starch is unstable and typically requires cooking and make down dilution, and exhibits sporadic performance.

Latex can have repulpability and nozzle plugging issues.

Controlling ply bonding is important and difficult.

Inadequate, excessive, or inconsistent ply bonding can jam complex, high-speed machinery, generate high waste, and provide unacceptable product.

While bonding by embossing sometimes can be improved by increasing the pressure on the embossing rolls, such pressure can wear out the embossing rolls more quickly, particularly the female roll, which is usually a softer roll made of composite material onto which a pattern is impressed by the opposing, male, engraved metal roll.

In addition, the journals and bearings of both embossing rolls can also wear out prematurely if subjected to increased pressure over a prolonged period.

Creping adhesives overcome some of the problems of embossing, but they also cause problems, such as “through bonding” or “blocking”, in which adjacent laminates bond to one another, and, prevent unwinding of the laminate product from its roll.

Non-uniformity of bonding also causes problems, such as wrinkling of the tissue and bad printing.

Low wet strength napkins may pull apart when subjected to moisture, such as spilled liquid or a wet glass, rendering them unsatisfactory for the high quality markets.

Floating plies at the printing stage cause jams, high waste and machine downtime.

In addition, the application of the ink causes the top layer of the tissue to expand if the plies are not well bonded, resulting in wrinkling, badly printed napkins, and extremely high costs from waste.

While a number of creping and ply bonding adhesives have been disclosed and are suitable for their intended uses, no single adhesive or adhesive blend has provided a satisfactory combination of adhesive performance characteristics (i.e. insolubility, rewet, adhesion and hardness) on different creping machines.

Images