The disclosure provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.

The disclosure provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.

The present invention concerns a process of making paper, board or paperboard in which a cellulosic thin stock is provided and subjected to one or more shear stages and then drained on a moving screen to form a sheet which is dried, wherein the process employs a treatment system which is applied to the thin stock, said treatment system comprising as components, a) a cationic organic polymer of charge density of at least 3.0 meq/g with a molar mass Mw of up to 3 million Daltons or poly aluminum chloride (PAC), b) a cationic polymer having an average molar mass Mw of at least 500,000 Daltons and a charge density not exceeding 4.0 meq/g; c) a microparticulate material; in which components (b) and (c) are added to the cellulosic thin stock after the last shear stage before the head box and component (a) is added to the cellulosic thin stock before the said last shear stage.

The present invention concerns a process of making paper, board or paperboard in which a cellulosic thin stock is provided and subjected to one or more shear stages and then drained on a moving screen to form a sheet which is dried, wherein the process employs a treatment system which is applied to the thin stock, said treatment system comprising as components, a) a cationic organic polymer of charge density of at least 3.0 meq/g with a molar mass Mw of up to 3 million Daltons or poly aluminum chloride (PAC), b) a cationic polymer having an average molar mass Mw of at least 500,000 Daltons and a charge density not exceeding 4.0 meq/g; c) a microparticulate material; in which components (b) and (c) are added to the cellulosic thin stock after the last shear stage before the head box and component (a) is added to the cellulosic thin stock before the said last shear stage.

In some embodiments, a process can include combining a plurality of fibers and water to produce a slurry, forming the slurry into a wet paper web, pressing and draining the wet paper web to produce a wet paper sheet, and drying the wet paper sheet to produce a paper product. A strengthening agent can be combined with the fibers and water to produce the slurry, applied to the wet paper web, and/or applied to the wet paper sheet. The strengthening agent can include a polyamidoamine-epihalohydrin resin and an additive. The additive can include a tannin and/or a compound having a chemical formula (I) of:

##STR00001##

where: R.sub.1, R.sub.2, and R.sub.3 can independently be a hydroxyl group or a methoxy group, and R.sub.4, R.sub.5, and R.sub.6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, or a CCCOOH group.

In some embodiments, a process can include combining a plurality of fibers and water to produce a slurry, forming the slurry into a wet paper web, pressing and draining the wet paper web to produce a wet paper sheet, and drying the wet paper sheet to produce a paper product. A strengthening agent can be combined with the fibers and water to produce the slurry, applied to the wet paper web, and/or applied to the wet paper sheet. The strengthening agent can include a polyamidoamine-epihalohydrin resin and an additive. The additive can include a tannin and/or a compound having a chemical formula (I) of:

##STR00001##

where: R.sub.1, R.sub.2, and R.sub.3 can independently be a hydroxyl group or a methoxy group, and R.sub.4, R.sub.5, and R.sub.6 can independently be H, an alkyl group, an aldehyde group, a carboxylic acid group, or a CCCOOH group.

The invention provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.

The invention provides methods and compositions for increasing the dry strength of paper. The invention utilizes a tailored strength agent whose size and shape is tailored to fit into the junction points between flocs of a paper sheet. The strength agents is in contact with the slurry for just enough time to collect at the junction points but not so much that it can migrate away from there.