FI105117B - release Paper - Google Patents

Description

105117

The release paper

The present invention relates to paper designed to be used as release liner for industrial and consumer applications. Release papers 5 have a low surface energy and have previously been made by treating base paper with various silicone compounds because they effectively reduce surface energy. However, in certain areas, such as the automotive industry, silicone residues can cause damage.

The object of the invention is a release paper which does not contain silicone chemicals as release agent. This object is achieved by using a water-soluble or water-dispersible organic fluorochemical as a constituent of paper, either on the surface of the base paper and / or mixed with the fibrous raw material of the base paper. Both treatments on the same paper are also possible. The organic fluorochemical contains at least one fluoroaliphatic group. The fluoroaliphatic group is relatively short-chain compared to e.g. fluorinated polymer chains such as PTFE.

The paper may be kraft paper or the like which, after treatment, provides the paper with release properties for use in the applications mentioned below. The treatment can be carried out either directly in a paper machine or separately in a coating or finishing machine.

The release paper base paper typically has a fibrous composition of 40 to 100% 25 softwood pulp (pine and spruce with a mixture ranging from 100% fir to 100% pine) and 0 to 60% hardwood sulphate pulp, typically birch or eucalyptus. The bleaching of the base paper stock can be carried out in a so-called. ECF or TCF. Unbleached paper can also be used. The milling of the paper raw material takes place either in high consistency refining (HCR) at a dry content of 20-35% or in low consistency refining (LCR) at a dry content of 3-10%. However, the invention is not limited to the pulp materials mentioned above.

According to the invention, the paper is treated with a fluorochemical either by adding it to the wet end in the pulp step or by surface treatment on paper which has already undergone formation in a papermaking machine.

105117

The fluorochemical may be any of the products commercially available under the tradenames Scotchban FC 807, Scotchban FC 845, Asahi Guard 530, Asahi Guard 550, Zonyl RP Paper Fluoridizer, Foraperle and Bay-synthol FCP.

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A fluorochemical comprises water-soluble or water-dispersible organic compounds containing a fluoroaliphatic group. The "water-soluble" or "water-dispersible" property means that the compound can be applied by means of an aqueous carrier either to the fiber web pin 10 or within the fibrous web and permanently adheres to or on the fibrous web.

The compound has at least one fluoroaliphatic chain attached to a functional group, in particular an acid group, which can form 15 anions.

A typical compound has the general formula (I) (R f -X 1 A (O-M +) m (I) 20 where R f is a perfluoroalkyl radical, X is a bivalent linking radical containing alkylene alone or in combination with one or more heteroatoms, and A is an acid functional group such as a carboxylic or phosphoric acid group, whereby CT ~ represents the -OH group of the acid 25. In the case of a carboxylic acid, (Rf-X) may be attached ·: · directly to the carbon of the carboxylic acid backbone. X) it may be attached to phosphorus by an ester linkage of phosphoric acid m is typically 1 or 2 and n is 1 or 2, and if A represents a phosphate, m + n = 3. M + is a monofunctional cation, most preferably ammonium or amine.

The perfluoroalkyl radical Rf typically comprises 3 to 18 carbon atoms, preferably 4 to 12, being of the type CnF 2n + 1. wherein n is 3-18, preferably 4-12.

The most preferred products may be described as salts of perfluoroalkyl phosphates, in particular ammonium or amine salts, e.g. ethyl) phosphate salts, in particular their ammonium salts. These compounds are characterized in that they do not contain organic polysiloxane groups and are thus silicone-free.

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In the case of surface treatment, it can be done on a paper machine or after finishing. Conventional surface treatment methods such as adhesive press coating, film press coating, or the like may be used to apply the agent to the paper surface.

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The fluorochemical surface treatment may also include natural polymers or binders derived from natural polymers, such as starch binders, typically naturally occurring, oxidized or cationic starches or corresponding starch esters or ethers, or carboxymethyl cellulose. The surface treatment may also include mixtures of synthetic binders, such as styrene butadiene latex, polyvinyl alcohols, polyvinyl acetate, acrylic latex, or mixtures thereof.

The viscosities of the surface treatment compositions can range from 20 to 1500 mPas at 50 ° C as measured by a Brookfield viscometer at 100 rpm.

For surface treatment, the typical amount of fluorochemical added may vary from 1 to 10 g / m2 of dry matter, based on the surface area of the base paper. 25 The mixing ratio of chemicals may vary as follows: natural binder ... 0-90%, fluorochemical 10-100%, synthetic binder 0-90%.

The total amount of binder-containing surface treatment composition may range from 1 to 20 g / m 2.

30 If the fluorochemical is added to the pulp before papermaking, it may be present in an amount of 1 to 10 g / m2 of dry matter for every 100 g / m2 of final product.

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It is also possible to add the fluorochemical both to the pulp before and after pa-35 formation, as a surface addition on the same paper, using a suitable combination of the above amounts.

The final release paper is characterized by the following typical values: 4,705,777

test method

Gross weight (g / m2) 83 ISO 536

The tensile index MD (Nm / g) 113 IS01924 CD (Nm / g) 50 IS01924

Tensile Strength MD (kN / m) 9.3 IS01924 CD (kN / m) 4.2 IS01924

Air Resistance (s) 530 ISO 3687

Tear Index MD (mNm2 / g) 7.8 IS01974 CD (mNm2 / g) 9.0 IS01974

Tear Strength MD (mN) 650 IS01974 CD (mN) 750 IS01974

Breaking strength (kPa) 450 ISO 2758

Kit value ts 10 3M method ws 14

Brightness (%) 85 ISO 2470

Notes: MD = machine direction, CD = cross direction.

The final product may have a basis weight of 50-200 g / m2, in particular 80-150 g / m2. The tensile index may be in the machine direction 60-140 and in the transverse direction 40-60, and the tear index in both the machine direction and the transverse direction 6-13. The air resistance can range from 30 to 2000. The test methods and units are the same as described above.

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The surface coating containing the fluorochemical as a release agent may extend evenly over the entire base paper or the release paper product may have discrete areas of this coating.

The surface energy of the final product is typically between 6 and 10 dyn / cm.

The paper can be made on a single or double wire machine.

5, 705777

As a fluorochemical, one compound of formula I or a mixture of compounds which are commercially available may be used.

All of the above numerical values are given by weight (wt%).

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The invention is not limited to the above examples but may vary within the scope of the appended claims.

The release paper of the invention can be used in a number of applications where it is intended to be positioned against a different surface and to be easily detached from this surface without leaving any residue on the surface.

Typical end-uses for the release liner according to the invention are au-15 practice abrasive papers, self-adhesive label release liners, and adhesive tape release liners, but the invention is not limited to these end-uses only.

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Claims (11)

1. Release paper comprising a release substance, characterized in that the paper contains water-soluble or water-dispersible organic fluorochemical comprising a compound containing at least one fluoroaliphatic group. 2. Release paper according to claim 1, characterized in that the paper contains fluorochemicals as an additive at the liquid end. 10 Release paper according to claim 1 or 2, characterized in that the paper contains fluorochemical as a surface treatment. 4. Release paper according to claim 3, characterized in that the paper 15 contains adhesives in connection with the fluorochemical as a surface treatment. 5. Release paper according to claim 4, characterized in that the binding agents are biopolymers or their derivatives, such as starch-based binders or carboxymethyl cellulose. 6. Release paper according to claim 4, characterized in that the binding agents are synthetic binders, such as styrene butadiene latex, polyvinyl alcohol, polyvinyl acetate, acrylic latex, or mixtures thereof. 25 Release paper according to any one of claims 1 to 6, characterized in that the fluoroaliphatic group contains a perfluoroalkyl group. Release paper according to any of claims 1 to 7, characterized in that the fluoroaliphatic group is bonded to a functional group, in particular a salt-forming acid group. 9. Release paper according to claim 8, characterized in that the fluorochemical comprises a perfluoroalkyl phosphate site. 9 105777 Release paper according to any one of claims 1 to 9, characterized in that the amount of the fluorochemical is from 1 to 10 g / m 2 of dry substance in the surface treatment and / or 1 to 10 g / m 2 of dry substance per 100 g / m 2 of the final weight of the final product. 5 Release paper according to any of claims 1 to 10, characterized in that its surface weight is 5Q-200 g / m2, in particular 80-150 g / m2. • «* * r