SE542116C2 - Method of producing a hollow synthetic bristle, a hollow synthetic bristle and a paint brush comprising such hollow synthetic bristles - Google Patents

Abstract

The present invention concerns a method of producing a hollow synthetic bristle (1) for a paint brush. A cross-sectional area of the hollow synthetic bristle is cylindrical or oval shaped or S-shaped and the hollow synthetic bristle has an approximate even wall thickness along the length of the synthetic bristle before being chemically tipped. The method comprises: arranging a first end of the hollow synthetic bristle (1) in a holder; immersing a part (2) of a second end of the hollow synthetic bristle (1) in a chemically tipping fluid, and lifting up the hollow synthetic bristle (1) from the chemically tipping fluid after a period of time. The part (2) of the hollow synthetic bristle (1) that is immersed in the chemically tipping fluid is 1-30% of the length of the hollow synthetic bristle (1).

Description

Method of producing a hollow synthetic bristle, a hollow synthetic bristle and a paint brush comprising such hollow synthetic bristles TECHNICAL FIELD The present invention relates to a method of producing a hollow synthetic bristle, a hollow synthetic bristle and a paint brush comprising a plurality of such hollow synthetic bristles.

BACKGROUND ART Synthetic bristles, i.e. monofilaments, can be produced from a wide variety of thermoplastic polymers, in a wide variety of configurations including solid and hollow, and in a wide variety of cross-sections, including circular, oval, triangular, trilocular, tetralocular, lobate, or may contain multiple voids. Much work has been done in the trade to improve paint pickup and paint release of paint brushes by experimenting with blends of different polymers, configurations, and cross-sections.

Natural fibres having split ends are known to hold paint more effectively and the multitude of small hairs at the tip section of each bristle to create a finer, smoother surface finish.

Hollow paint brush synthetic bristles have become more and more popular since they have a good paint pick up. However, no hollow synthetic bristles providing a similar efficiency as the natural fibres regarding the combination of holding paint and creating a finer surface finish has yet been satisfactorily achieved.

SUMMARY OF THE INVENTION Finish treatment or processing of the tip section of synthetic bristles, i.e. tipping can be achieved mechanically or chemically. Mechanical tipping can be achieved by passing the bristle over a rotating grindstone. Chemical tipping can be achieved by dipping an end portion of a bristle or bundle of bristles into a chemical tipping fluid, such as a caustic base or acid , to a certain bristle and/or bundle depth.

By "tipping" is throughout this document hereby meant any processing or finish treatment suitable to be applied to a tip section of a synthetic bristle, such as tapering and flagging.

It is commonly known within the technical field that hollow synthetic bristles cannot be satisfactorily tipped by means of chemical tipping, because of the capillary action drawing the chemical tipping fluid into a non-controllable inside depth of the hollow synthetic bristle. A disadvantage with mechanical tipping is that hollow synthetic bristles are readily damaged when subjected to known commercial tipping machines.

Furthermore, it is commonly known that paint brushes having synthetic bristles are easier to clean and usually are less expensive than paint brushes having natural fibres.

It is, accordingly, an object of the present invention to overcome deficiencies of the prior art, such as indicated above.

It is another object to provide improved paint brush hollow synthetic bristles having satisfactorily tipped sections which to a greater extent simulate natural fibres with split ends.

It is yet another object of the invention to provide a process for making a satisfactorily tipped section of a hollow synthetic bristle.

It is still another object of the invention to provide superior paint brush synthetic bristles having an improved paint pickup and paint release as well as create a fine and smooth surface finish.

Another object of the invention is to provide paint brush synthetic bristles with optimised performance/characteristics, e.g. in regard of tailored stiffness, i.e. lower stiffness at their tips and higher stiffness closer to their roots.

It is a further object of the present invention to provide a tapered and/or flagged synthetic bristle useful in the manufacture of paint brushes and having an improved paint pickup, paint release and which create a fine and smooth surface finish.

A further object of the present invention is to provide a method of chemically flagging/fraying free ends of hollow synthetic bristles such that their free ends are flagged/fringed "enough", i.e. not too much or too little. Hence, after finishing the treatment/method their free ends comprise an optimised shape and/or number and/or size of useful split ends/frays being two, three or a plurality of smaller and/or fractional ends at the free end section of each hollow synthetic bristle and to provide such inventive hollow synthetic bristles for manufacture of paint brushes. In principle, the method according to the invention make the free ends of the hollow synthetic bristles tattered and torn by chemically dividing them/splitting them up/disunite them into more and smaller free ends out of one larger free end. These hollow synthetic bristles, each comprising a multi-tipped free end, i.e. a free end comprising at least two "micro" tips, instead of only one "macro" tip, accomplishing improved paint pickup, paint release and fine and smooth surface finish.

According to the invention a method of producing a hollow synthetic bristle for a paint brush is provided, wherein a cross-sectional area of the hollow synthetic bristle is cylindrical or oval shaped or S-shaped and the hollow synthetic bristle has an approximate even wall thickness along the length of the synthetic bristle before being chemically tipped and wherein the method comprises arranging a first end of the hollow synthetic bristle in a holder; immersing a part of a second end of the hollow synthetic bristle in a chemically tipping fluid; lifting up the hollow synthetic bristle from the chemically tipping fluid after a period of time, and wherein the part of the hollow synthetic bristle that is immersed in the chemically tipping fluid is 1-30% of the length of the hollow synthetic bristle.

Hereby is provided a finish treatment or processing of the free or second end of the hollow synthetic bristle, including chemical tipping of between 1 - 30% of the length of the hollow synthetic bristle.

Furthermore is provided a finish treatment or processing wherein the part of the second end of the hollow synthetic bristle is being processed on both its inside and outside.

In the context of the present invention under the term "bristle" there is understood an elongated flexible body having a first end and a second end. The first end is part of a root section where the bristle may be contained in and/or fastened in a bristle carrier. The second end of the bristle forms a free tip which usually contacts a surface to be coated with paint. The second end is part of a tip section of the bristle.

The hollow synthetic bristle may be produced from a wide variety of thermoplastic polymers, such as polyamides, polyesters and polyolefins.

The hollow synthetic bristle may be between 40 - 100 mm long.

The hollow synthetic bristle may comprise one or more longitudinal cavities extending from an opening in the free or second end of the synthetic bristle toward the first end of the synthetic bristle. The one or more longitudinal cavities may extend along a part of the length of the synthetic bristle or along the whole length of the synthetic bristle making the synthetic bristle partly hollow along its length or hollow along its full length similar to a tube. Moreover, the one or more longitudinal cavities may, but do not have to, be in exact alignment with the central axis of the synthetic bristle. Such a cavity may also extend at an angle relative the longitudinal extension and the extension of the central axis of a synthetic bristle.

Experiments have shown that by applying the chemical tipping to a shorter end portion of the synthetic bristle than conventionally done when using chemically tipping on solid bristles, usually about 25 mm of the tip section or up to 50% of the length of prior art bristles, a method is provided which allows the use of chemical tipping on a hollow synthetic bristle, as the problem of capillary action drawing tipping fluid into a non-controllable inside depth of the synthetic bristle is avoided. Experiments also show that uncontrollable suction and/or capillary effect is reduced as the hollow synthetic bristle in some aspects "lets go" of the paint inside its cavity as the paint is not fully enclosed, at least not circumferentially. This is due to that the hollow synthetic bristle is at least in some aspects partly open along its envelope surface of its free end after treatment according to the invention such that the paint does not "cling" too firmly to the free end, i.e. the capillary action has less firm "grip"/capillary holding effect of the paint as hitherto in prior art.

Hereby is provided a hollow synthetic bristle having a satisfactorily tipped section. The tip section corresponding to the part of the second end of the hollow synthetic bristle being immersed in the chemically tipping fluid.

Furthermore, the chemical tipping reduces the wall thickness of the hollow synthetic bristle on both its outside and inside surface. Hence, the reduced wall thickness obtained by tipping the outside surface of the hollow synthetic bristle provides a tapered synthetic bristle. Hence, also the reduced wall thickness obtained by tipping the inside surface of the hollow synthetic bristle provides a larger hollow cavity within the tipped part of the synthetic bristle which accommodates an increased capability of paint pickup.

Furthermore, the chemical tipping flag the tipped part of the hollow synthetic bristle into a plurality of split ends or tips, which accommodates a further increased capability of paint pickup, paint release and creation of a fine and smooth surface finish.

In principle, the method according to the invention make the free ends of the hollow synthetic bristles tattered and torn by chemically dividing them/splitting them up/disunite them into more and smaller free ends out of one larger free end. These hollow synthetic bristles, each comprising a multi-tipped free end, i.e. a free end comprising at least two "micro" tips, instead of only one "macro" tip.

In one aspect of the invention the part of the hollow synthetic bristle that is immersed in the chemically tipping fluid is 10 - 30%, 10 - 25% or 10 - 20% of the length of hollow synthetic bristle.

In another aspect of the invention the length of the part of the hollow synthetic bristle that is immersed in the chemically tipping fluid is 1 - 20 mm, 5 - 15 mm or about 10 mm.

In yet another aspect of the invention the chemically tipping fluid comprises sodium hydroxide (NaOH). The method may thereby comprise applying a chemically tipping fluid, which may be a sodium hydroxide, to the part of the second end of the hollow synthetic bristle.

The chemically tipping fluid may be a sodium hydroxide solution or any other suitable dye being highly soluble in water producing a caustic basic solution. The sodium hydroxide solution may comprise 30 - 40% sodium hydroxide and 60 - 70% water and be heated to approximately 100 C°.

The chemical tipping may be provided by immersing the part of the second end of the hollow synthetic bristle one or more times into the chemically tipping fluid, such as the sodium hydroxide solution.

The chemical tipping may be provided by immersing the part of the second end of the hollow synthetic bristle with a varying depth/distance into the chemically tipping fluid during the time duration in the tipping fluid. The immersed part of the second end of the hollow synthetic bristle may be lifted up and down in tipping fluid at different time rates and/or velocities and/or stepwise. It may be held immersed at different depths and with varying duration at each depth or immersed in steps and with varying depth and/or held immersed with the same or different duration at each step.

In another aspect of the invention a wall thickness of the hollow synthetic bristle is from about 0.05 - 0.1 mm and/or between 0.05 - 0.1 mm.

The chemically tipped part of the second end of the synthetic bristle may comprise a thinner wall thickness compared to the non-tipped remaining part of the synthetic bristle.

The hollow synthetic bristle(s) may be dipped into the chemically tipping solution, such as the sodium hydroxide solution, preferably in between 30 - 60 minutes and/or about 30 minutes and/or about 60 minutes or for a period of time being more or less.

In one aspect of the invention, lifting up the hollow synthetic bristle from the chemically tipping fluid is made after such a period of time that the part of the hollow synthetic bristle has been partly decomposed in the chemically tipping fluid.

In another aspect of the invention, lifting up the hollow synthetic bristle from the chemically tipping fluid is made after such a period of time that longitudinal parts of the hollow synthetic bristle has been decomposed in the chemically tipping fluid and the second end of the hollow synthetic bristle has two or more tips.

In yet another aspect of the invention, the period of time is such that 1 - 30% of the part of the hollow synthetic bristle that is immersed in the chemically tipping fluid is decomposed in the chemically tipping fluid.

In one aspect of the invention, the method further comprising immersing the second end of the hollow synthetic bristle in water after it has been lifted up from the chemically tipping fluid.

In another aspect of the invention, the hollow synthetic bristle is a hollow polyester bristle.

In yet another aspect of the invention, the method further comprises the step of drying the hollow synthetic bristle.

The invention also relates to a hollow synthetic bristle obtained by the above method.

The invention also relates to a paint brush comprising a plurality of hollow synthetic bristles as described above. Hereby is provided a paint brush having an improved paint pickup and paint release.

The paint brush may comprise a handle, a bristle carrier and a plurality of bristles attached to the handle by means of an adhesive and/or the bristle carrier and/or any other suitable fastening means.

The paint brush may comprise a blend of different types of natural and/or synthetic bristles, wherein a first type of synthetic bristles is the hollow synthetic bristles as described above.

The different types of bristles may include solid and hollow bristles or partly solid/hollow bristles, in a wide variety of cross-sections, including circular, oval, triangular, trilocular, tetralocular, lobate, and/or may contain multiple voids, be corrugated and/or have other structured surfaces. Furthermore the different types of bristles may include bristles being mechanically and/or chemically tipped.

BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be explained in further details with reference to the drawings showing an aspect thereof.

Fig. 1a shows a chemically tipped hollow synthetic bristle according to the invention, Fig. 1b shows a cross-sectional view (A-A) of the synthetic bristle in Fig. la, Fig. 2 shows a chemically tipped hollow synthetic bristle being flagged, and Fig. 3 shows steps of a method of producing the hollow synthetic bristle(s) according to the invention.

DETAILED DESCRIPTION The present invention relates to a hollow synthetic bristle 1 to be used together with several other synthetic bristles being the same, similar or different as a plurality or a bundle or mixture of synthetic bristles with at least one such inventive hollow synthetic bristle, preferably more than one, in paint brushes (not shown) and a paint brush comprising a plurality of such synthetic bristles 1. The present invention also relates to a method of forming/shaping the synthetic bristle 1, i.e. at least a part of its free end, i.e. its second end.

Figs, la-lb show a synthetic bristle 1 according to the invention. Referring to Fig. la, a chemically tipped hollow synthetic bristle 1 according to the invention is illustrated wherein the synthetic bristle 1 is divided into a part 2 of the second end, i.e. a tipped section, and a remaining part 4, i.e. a non-tipped section, extending from a first end (not shown) of the hollow synthetic bristle towards part 2 of the second end. The tipped part 2 extends from the non-tipped remaining part 4 towards an opening 5 at the second end. The tipped part 2 is part of the free end of the hollow synthetic bristle 1. The hollow synthetic bristle 1 may be a tubular synthetic bristle 1 comprising a longitudinal cavity 6 extending from the opening 5 along the length of the synthetic bristle. The longitudinal cavity 6 may as in the presently illustrated aspect be cylindrical, or have any other suitable shape. The longitudinal cavity 6 may as in the presently illustrated aspect be an inner cavity extending along the length of the synthetic bristle. If the hollow synthetic bristle 1 is oval-shaped in cross-section the longitudinal cavity 6 may have a corresponding oval shape. The hollow synthetic bristle 1 may be made from polyester and the non-tipped remaining part 4 may have an outer diameter between 0.2 - 0,4 mm. The tipped part 2 of the second end of the synthetic bristle comprises 1 - 30% or 10 - 30% or 10 - 25% of the total length of the synthetic bristle 1. Alternatively the tipped part 2 of the second end of the synthetic bristle 1 comprises 10 - 20% of the total length of the synthetic bristle. The wall thickness of the non-tipped remaining part 4 may be between 0.05 - 0.1 mm and the wall thickness of the tipped part 2 of the second end may be between 0.05 - 0.1 mm. In some aspects, the wall thickness of tipped part 2 of the second end is less than the wall thickness of non-tipped remaining part 4.

Referring to Fig. 1b, a cross-section A-A of the chemically tipped hollow synthetic bristle 1 of Fig. 1a is shown, wherein the applied chemical tipping has reduced the wall thickness of both the inside and the outside surface of tipped part 2 of the second end of the hollow synthetic bristle 1. Hereby is provided a tapered synthetic bristle 1 having a longitudinal cavity 6 which cross-sectional area of the bristle wall is decreased in the tipped part 2 of the second end of the hollow synthetic bristle 1 being immersed into a chemically tipping fluid. The crosssectional area of the cavity 6 is larger in the tipped part 2 of the second end of the hollow synthetic bristle 1 than in the non-tipped remaining part 4 of the hollow synthetic bristle 1, wherein the cross-sectional area of the cavity 6 may be largest at the opening 5. The tipped part 2 of the hollow synthetic bristle 1 may transition into the non-tipped remaining part 4, i.e. as seen in the direction from the second or free end and its opening 5 towards the non-tipped remaining part 4 of the hollow synthetic bristle 1.

Referring to Fig. 2, a chemically tipped hollow synthetic bristle 1 being flagged according to the invention is illustrated wherein the hollow synthetic bristle 1 has been provided with a plurality of split ends or tips 7. The tips 7 are provided by the chemically tipping fluid decomposing longitudinal parts along the length of the hollow synthetic bristle 1 in the second end of the hollow synthetic bristle 1.

The tipped part 2 of the second end of the hollow synthetic bristle 1 may be both tapered and flagged when being chemically tipped, i.e. when applying the method of producing the hollow synthetic bristle 1 according to the invention. In some aspects due to the fact that the chemical tipping corrodes through the wall of at least a part of the tipped part 2, i.e. the resulting "pit depth" of the corrosion exceeds its wall thickness, in principle a chemical flagging or cutting up or cutting "open" the tipped section 2 into more than one small end or tip 7 is accomplished.

Referring to Fig. 3, the steps A - D of a method of producing a hollow synthetic bristle 1 according to the invention is illustrated, wherein a first step A comprises arranging the first end (not shown) of the hollow synthetic bristle 1 in a holder (not shown).

The following step B comprises immersing the part 2 to be tipped of the second end of the hollow synthetic bristle 1 in a chemically tipping fluid, wherein part 2 to be tipped of the second end of the hollow synthetic bristle 1 may make up 1 - 30% or 10 - 30% or 10 - 25% or second end of the hollow synthetic bristle 1 may make up 1 - 20 mm, 5 - 15 mm or about 10 mm of the length of hollow synthetic bristle 1.

The following step C comprises lifting up the hollow synthetic bristle 1 from the chemically tipping fluid after a period of time, wherein the period of time may be in between 30 - 60 minutes and/or about 30 minutes and/or about 60 minutes or for a period of time being more or less.

Step D and E are both optional steps wherein one of them or both may be performed after step C. Step D comprises immersing the second end of the hollow synthetic bristle 1 in water or any other suitable cleaning liquid after it has been lifted up from the chemically tipping fluid and step E comprises drying the hollow synthetic bristle 1. Step D is done to rinse or wash off the tipping fluid from the hollow synthetic bristle 1 before further use. Purpose of step E is self-explanatory.

Claims (13)

1. Method of producing a hollow synthetic bristle (1) for a paint brush, wherein a cross-sectional area of the hollow synthetic bristle is cylindrical or oval shaped or S-shaped and the hollow synthetic bristle has an approximate even wall thickness along the length of the synthetic bristle before being chemically tipped and wherein the method comprises; arranging a first end of the hollow synthetic bristle (1) in a holder, immersing a part (2) of a second end of the hollow synthetic bristle (1) in a chemically tipping fluid, lifting up the hollow synthetic bristle (1) from the chemically tipping fluid after a period of time, wherein the part (2) of the hollow synthetic bristle (1) that is immersed in the chemically tipping fluid is 1-30% of the length of the hollow synthetic bristle (1).

2. Method according to claim 1, wherein the part (2) of the hollow synthetic bristle (1) that is immersed in the chemically tipping fluid is 10 - 30%, 10 - 25% or 10 - 20% of the length of the hollow synthetic bristle (1).

3. Method according to claim 1 or 2, wherein the length of the part (2) of the hollow synthetic bristle (1) that is immersed in the chemically tipping fluid is 1 - 20 mm, 5 - 15 mm or about 10 mm.

4. Method according to any of the preceding claims, wherein the chemically tipping fluid comprises sodium hydroxide (NaOH).

5. Method according to any of the preceding claims, wherein a wall thickness of the hollow synthetic bristle (1) is 0.05 - 0.1 mm.

6. Method according to any of the preceding claims, wherein lifting up the hollow synthetic bristle (1) from the chemically tipping fluid is made after such a period of time that the part (2) of the hollow synthetic bristle (1) has been partly decomposed in the chemically tipping fluid.

7. Method according to any of the preceding claims, wherein lifting up the hollow synthetic bristle (1) from the chemically tipping fluid is made after such a period of time that longitudinal parts of the hollow synthetic bristle (1) has been decomposed in the chemically tipping fluid and the second end of the hollow synthetic bristle (1) has two or more tips (7).

8. Method according to any of the preceding claims, wherein the period of time is such that 1 -30% of the part (2) of the hollow synthetic bristle (1) that is immersed in the chemically tipping fluid is decomposed in the chemically tipping fluid.

9. Method according to any of the preceding claims, further comprising immersing the second end of the hollow synthetic bristle (1) in water after it has been lifted up from the chemically tipping fluid.

10. Method according to any of the preceding claims, wherein the hollow synthetic bristle (1) is a hollow polyester bristle (1).

11. Method according to any of the preceding claims, further comprising the step of drying the hollow synthetic bristle (1).

12. A hollow synthetic bristle (1) for a paint brush obtained by the method according to any of claims 1 to 11.

13. A paint brush comprising a plurality of hollow synthetic bristles (1) according to claim 12.