Pen having an integrally injection-moulded coating sleeve

Abstract

A pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic, wherein the casing, respectively viewed in the radial direction, has an outer enrichment zone with a higher concentration of the first plastic than in the middle region and the casing, respectively viewed in the radial direction, has an inner enrichment zone with a higher concentration of the first plastic than in the middle region.

Claims

1. A pencil for applying a coloring and/or cosmetic substance, comprising: a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic that are mixed with each other; wherein the casing, respectively viewed in a radial direction, has an outer enrichment zone with a higher concentration of the first plastic than in a middle region of the casing; and the casing, respectively viewed in the radial direction, has an inner enrichment zone with a higher concentration of the first plastic than in the middle region.

2. The pencil of claim 1, wherein the concentration of the first plastic decreases continuously from the outer enrichment zone and from the inner enrichment zone toward the middle region.

3. The pencil of claim 1, wherein over at least 80% of its cross-section area, the plastic casing is composed of both the first and the second plastics, with the two plastics being encountered in percentages by weight that differ by location.

4. The pencil of claim 1, wherein the casing consists predominantly, at least 85% by weight, of the first and second plastics, plus any fillers and auxiliary materials such as pigments.

5. The pencil of claim 1, wherein one of the first and second plastics is a weakly polar plastic with an electron negativity difference EN in the range 0.3EN0.5.

6. The pencil of claim 1, wherein one of the first and second plastics is a strongly polar plastic with an electron negativity difference EN in the range 0.5<EN1.7.

7. The pencil of claim 1, wherein the first plastic is an AES.

8. The pencil of claim 1, wherein the second plastic is a TPE.

9. The pencil of claim 1, wherein the thermoplastic material comprising the casing is set up so that the first plastic has a weight proportion of at least 45% by weight.

10. The pencil of claim 1, wherein an upper limit for the first plastic in the injection-ready mix is 85% by weight.

11. The pencil of claim 1, wherein at an outer circumference surface, the casing has a mathematically determined gloss level GU of more than 30 GU.

12. The pencil of claim 1, wherein the casing has a structure composed of two layers that can be separated from each other.

13. The pencil of claim 1, wherein the plastic casing consists of a non-foamed plastic.

14. The pencil of claim 1, wherein the casing is embodied in the form of a tube that is open at both ends.

15. The pencil of claim 1, wherein at one end, the casing tapers conically.

16. The pencil of claim 1, wherein at one end, the casing has a shoulder with a reduced diameter.

17. The pencil of claim 1, wherein at an end of the pencil, an end cap is fastened; which closes one end of the casing.

18. A method for producing a pencil with a casing according to claim 1, comprising the steps of: a plasticized, injection-moldable compound is produced, composed of a first and second plastic material that are completely mixed with each other, the plastic materials are chosen so that they have solidification behaviors that differ from each other such that they separate when they come into contact with a cooled mold surface, the compound is injected at a high pressure of at least 900 bar into a mold cavity of an injection mold forming the casing of the pencil, with the injection mold being intensively cooled such that directly against its wall surface that produces the mold cavity and over the entire length of the mold cavity, predominantly the first plastic material solidifies and is thus enriched against the wall surface, and then the two plastic materials in a region of the casing, which is underneath a region of an outer circumference surface of the casing, solidify together with less separation than in the region of the outer circumference surface or without any separation.

19. The method of claim 18, wherein in the region of the outer circumference surface of the casing, no mold parting line is formed by the injection mold.

20. The method of claim 18, wherein the completely injection molded casing is ejected from the mold in the direction of its longitudinal axis L.

21. The method of claim 18, wherein a pigment core receptacle in a center of the casing is formed by a pin that constitutes a mold core, which is removed together with the casing when the casing is ejected from the injection mold.

22. The method of claim 18, wherein the wall surface of the injection mold that forms the outer circumference surface of the casing has a roughness depth Rz5 m.

23. The method of claim 18, further comprising casting a pigment core, wherein the casing is inserted into a mold that seals the casing at a tapering end of the casing and that forms a subsequent shape of an unused tip of the pigment core, and a compound that forms the pigment core is poured in at the other end of the casing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows the casing of a pencil according to the present disclosure in a longitudinal section through the center.

(2) FIG. 2 shows the entire pencil according to the present disclosure in a longitudinal section through the center.

(3) FIG. 3 is an enlarged detail and shows a part of the fracture plane of a casing that has been torn apart along its longitudinal axis.

(4) FIG. 4 shows a section perpendicular to the central longitudinal axis through the casing of a pencil according to the present disclosure.

(5) FIG. 5a shows an overview of the skin detachment test at the beginning, after the incision.

(6) FIG. 5b shows a detailed view of the skin detachment test as it progresses further.

(7) FIG. 6 shows the respective RAMAN spectra for SAN and TPC-ET.

(8) FIG. 7 shows the RAMAN spectra for SAN and TPC-ET for the pure substances and at 2 different measurement points 100 and 200 on the sectional plane of the casing.

(9) FIG. 8 shows the RAMAN intensity of the spectra recorded for samples that contained 0% by weight SAN, 30% by weight SAN, 50% by weight SAN, 70% by weight SAN, and 100% by weight SAN and the complementary percentages of TPE-ET.

(10) FIG. 9 shows the steps in which the sectional plane of the casing, which was produced according to the 1.sup.st embodiment, was measured using RAMAN spectroscopy.

(11) FIG. 10 shows how the concentration of SAN and TPC-ET changes in the radial direction over the cross-section of the casing.

DETAILED DESCRIPTION

First Embodiment

(12) For the first embodiment, 60% by weight SAN (LURAN 378P) and 40% by weight TPC-ET (Arnitel EM400) with the addition of 3% pigments (preferably black pigments of the usual type carbon black CI 77266, which is available from various companies) are brought into the injection molding-ready, viscous state at a temperature of preferably 250 C.+/10 C. and are uniformly mixed in the process. No other fillers or auxiliary materials are added. An extruder from the company Leistritz, 90459 Nuremberg, Germany, can be used for this.

(13) The actual injection molding procedure can be carried out with an injection molding machine of the E-motion 940/160T type made by the company Engel, 90451 Nuremberg, Germany. The prepared compound is shot into the molding cavity of the injection mold at an injection pressure of approx. 1400 bar. The injection mold in this case is cooled by means of a liquid medium, which flows through the injection moldsealed off from the mold cavity. In particular, the core pin of the injection mold, which forms the cavity that is provided to subsequently accommodate the pigment core in the casing, is itself directly cooled by the liquid medium. In other words, the cooling medium flows through the core pin itself.

(14) Then the demolding is carried out, preferably by removing the core pin and the casing together from the mold cavity and then sliding the casing off of the core pin.

(15) The casing 2 produced in this way particularly preferably looks like the one shown in FIG. 1; the structural details of the casing 2 will be discussed in greater detail below.

(16) The casing produced in this way exhibits an extremely scratch-resistant outer circumference surface with a finish like a piano. It is very resistant to the migration of pigment core components and is easy to decorate.

(17) In order to obtain a cross-section that permits visual inspection, the casing 2 according to FIG. 1 was clamped into a tensile testing machine and torn into two halves by means of correspondingly high tensile forces in the direction along its longitudinal axis L. FIG. 3 shows an enlarged detail of the resulting fracture plane of the cross-section 3, in an initial visual assessment by microscope.

(18) It is already clear from FIG. 3 that a different layer has formed on and directly under the surface of the inner circumference 5 and the outer circumference 4. This finding was verified with measurements using RAMAN spectroscopy, as explained in detail below. The results of this are shown in FIG. 4.

(19) As is apparent, the one outer enrichment zone 6 and an inner enrichment zone 7 are discernible. The characteristics of the outer enrichment zone 6 and inner enrichment zone 7 can be influenced by means of the temperature of the surface that is produced inside the mold cavity. The colder the corresponding surface of the mold cavity is at the beginning of the injection, the more pronounced the separation is. This also applies to the inner enrichment zone 7. As already mentioned above, the temperature of the core pin that produces the inner enrichment zone can be controlled by providing a more or less intensive flow of the cooling medium through the core pin itself.

(20) In the present instance, within the limits of measurement accuracy using RAMAN spectroscopy, no amount of the second plastic can be found on the exposed surface of the outer enrichment zone. This is not only desirable in the context of this embodiment, but is also generally preferred. This is because such a formation is advantageous for achieving the glossy surface desired here, which resembles the finish of a piano. In the radially inward direction below the exposed surface, the percentage of the first plastic begins to decrease. Down to a depth of approximately 0.2 mm, however, a percentage of the first plastic of more than 90% by weight is present.

(21) It is interesting that in any case in the region of the outer enrichment zone, there appears to be a definite boundary layer starting at which the strength of the plastic that forms the wall of the casing decreases significantly. If a casing that has been produced according to this first embodiment is cut diagonally with a blade so that a diagonally protruding shaving is produced, as shown in FIGS. 5a and 5b, it is then possible to peel a skin off the surface of the casing by pulling on the shaving with the unaided hand, regardless of the depth of the cut. The skin is relatively strong and in most cases, only tears after a detachment length of 4 cm or more has been pulled off.

(22) In general, in a way that is applicable beyond this embodiment, it can be said that skin detachment tests of this kind have shown that a particularly good sharpenability is achieved whenever such skins can be pulled off with a thickness of 0.08 mm to 0.25 mm.

(23) To the extent that it has been possible to explain up to this point, it appears to be the case that the sharpener blade is then not reliant on having to completely cut the relatively strong skin and instead, it appears that a mix of cutting and tearing occurs, which has a facilitating effect.

Second Embodiment

(24) To produce the second embodiment, 60% by weight AES (ROTEC A702) and 40% by weight TPC-ET (Amitel EM400) with the addition of 3% pigments (preferably black pigments of the above-mentioned type) are brought into the injection molding-ready, viscous state at a temperature of preferably 250 C.+/10 C. and are uniformly mixed in the process. No other fillers or auxiliary materials are added.

(25) This compound, as described above for the first embodiment, is processed with the aid of the machines described therein, which is also true for the injection molding.

(26) The casing 2 produced in this way particularly preferably looks like the one shown in FIG. 1.

(27) The casing produced in this way exhibits an extremely scratch-resistant outer circumference surface with a silk-matt gloss. It is resistant to the migration of pigment core components and is easy to decorate.

(28) The tests using RAMAN spectroscopy, as will be explained in greater detail below, demonstrate that when this plastic mix is injection molded, a readily apparent outer enrichment zone and an inner enrichment zone that is just as readily apparent are formed, whose magnitude varies within the above-described ranges depending on the intensity of the cooling of the injection mold.

Comparison Example

(29) For the comparison example, 60% by weight SAN (LURAN 378P) and 40% by weight of a usually non-polar SBS block copolymer (ALLRUNA W55) with the addition of 3% pigments (preferably black pigments of the above-mentioned type) are brought into the injection molding-ready, viscous state at a temperature of preferably 250 C.+/10 C. and are uniformly mixed in the process. No other fillers or auxiliary materials are added. ALLRUNA W55 is a brand name of the company ALLOD Werkstoff GmbH & Co. KG, 91593 Burgbernheim, Germany.

(30) This compound, as described above for the first embodiment, is processed with the aid of the machines described therein, which is also true for the injection molding.

(31) The casing 2 produced in this way particularly preferably looks like the one shown in FIG. 1.

(32) The casing produced in this way exhibits a matte outer surface and neither a significant outer enrichment zone nor an inner enrichment zone. Instead, the materials remain homogeneously mixed until solidification. The skin detachment test also cannot be performed because the casing clearly has a homogeneous strength.

(33) RAMAN Spectroscopy for Determining Concentration

(34) For ascertaining the concentrations that are particularly found in the outer and inner enrichment zones according to the present disclosure, RAMAN spectroscopy is the method of choice.

(35) The above-described fracture plane turned out to be poorly suited to the performance of a RAMAN spectroscopy. Instead of this, the tests were performed on a cross-section that was produced by first cutting or sawing through the casing transversely to its longitudinal axis and the cross-section that had thus been exposed was then ground.

(36) To clarify the local proportions of SAN and TPC-ET, the RAMAN spectra were measured across the cross-section of the casing that had been produced according to the first embodiment. The measurement was performed with a RAMAN spectrometer from the Almega series produced by the company Thermo Fisher Scientific, 168 Third Avenue, Waltham, Mass. USA 02451.

(37) In order to calibrate the device and be able to assign the individual parts of each respective spectrum, first the raw materials were measured. In other words, plates were produced that consisted of up to 100% by weight SAN and up to 100% by weight TPC-ET. If a measuring point comes to rest fully on the respective plate and the thickness of the plate exceeds 2/10 mm, then the dimensions of the test pieces do not matter. Individual measurements were performed on the two plates by themselves.

(38) The spectra obtained in this way were plotted in the graph according to FIG. 6. The dot-and-dash line shows the spectrum recorded for SAN and the solid continuous line shows spectrum recorded for TPE-ET.

(39) The area of the peak that reaches its maximum at 3050 cm1 was used for the SAN ascertainment; the area of the peak whose maximum is at 2250 cm1, which is also characteristic for the SAN, could likewise be used; it yields comparable values and therefore does not have to be separately considered below and can instead be disregarded.

(40) Then the points 100 and 200 identified in FIG. 4 were measured one after the other. The two spectra recorded in this case were superposed as shown in FIG. 7. It is already clear from these figures that different concentrations of SAN and TPC-ET are found at the points 100 and 200.

(41) Then in addition to the above-mentioned samples containing 0% by weight and 100% by weight SAN, different mixes of SAN and TPC-ET are systematically produced and, through suitable temperature control, processed to produce the above-mentioned boundary layer-free plates, namely mixes that contained 30% by weight, 50% by weight, and 70% by weight SAN and the complementary percentages of TPC-ET. The RAMAN intensity of the spectra that were recorded for the individual representatives of this sample series were plotted in the graph that is shown in FIG. 8. In FIG. 8, it is clear that each mixing ratio can be assigned to a characteristic RAMAN intensity and there is a linear relationship between the percentage by weight of the SAN, the TPC-ET, and the respective RAMAN intensities that are to be measured for them.

(42) Thenas has been described abovethe ground cross-section of the casing 2, which was produced in accordance with the first embodiment, was measured in a way that matches the sequence shown in FIG. 9 step for step. Measurements were carried out point by point starting from the outside and continuing in the radial direction to the middle of the casing cross-section and carried out point by point starting from the inside and continuing in the radial direction to the middle of the casing cross-section.

(43) These measurements yield the graph that is shown in FIG. 10. The plastic compound used for the injection molding had a mixing ratio of SAN to TPC-ET. Starting from this and taking into consideration the spread of measurement results, it is evident that a partial separation has occurred during the injection molding process in the injection molding tool.

(44) In this case, the concentration of SAN at the surface of the outer circumference surface of the casing is approx. 100% by weight.

(45) At the surface of the inner circumference surface, the concentration of SAN is only approx. 70% by weight.

(46) The Structural Embodiment of the Pencil

(47) The pencil 1 according to the present disclosure is embodied as shown in FIGS. 2, 3, and 4. As a rule, it has an outer diameter of approx. 6 to 16 mm.

(48) At its center, it has a receptacle for the pigment core 8 that advantageously constitutes a form-fitting rotation prevention means. Its cross-section can be circular, but is preferably oval, polygonal, or octagonal in order to insure a better hold between the pigment core 8 and the casing 2. The distance between opposing flat sides of the octagon is preferably between 3 and 5 mm. The wall thickness of the casing 2 is preferably in the range from 1.5 to 3 mm. The length of the pencil 1, i.e. its length in the direction of its longitudinal axis L, is generally greater than 85 mm, usually greater than 100 mm, and up to 180 mm.

(49) The receptacle for the pigment core 8 preferably extends through the entire casing 2 in the direction of its longitudinal axis L, i.e. as a semifinished product, the casing 2 forms a tube. This facilitates the pigment core casting. This is because at the end at which it forms the cone that is to be described in greater detail below, the casing, for purposes of the pigment core casting, can be inserted into a mold that seals it shut and then in the same way, gives the end of the pigment core in the region of the cone a corresponding, as a rule likewise conically tapering, shape. The pigment core compound is then poured in from the other end of the casing at which the seat is located and fills the pigment core receptacle in the casing 2 and the mold cavity that models the tip of the pigment core 8. A casing consisting of plastic like the one according to the present disclosure can be inserted particularly well into a mold that closes it in a sealed fashion for purposes of the pigment core casting since the plastic of the casing, compared to a wooden casing, is reversibly elastic, i.e. can be inserted or clamped into a corresponding mold in a sealed fashion. The very smooth outer surface of the casing helps to achieve a reliable seal.

(50) The one end of the pencil 1 tapers to form a cone 12, preferably with a cone angle Pi of between 20 and 60. In this way, this end contributes to producing the sharpened end that is known from a normal wooden pencil and thus to form a starting surface, which in the first sharpening is correctly positioned relative to the sharpener blade and enables the sharpener blade to remove a shaving over its entire length.

(51) The other end of the pencil 1 preferably has a seat 9 in the form of a recessed region on its outer diameter. A closing cap 10 can be placed onto this seat and preferably, a detent engagement is produced between the seat 9 and the closing cap 10. In order to preserve the pigment core as much as possible and to prevent migrations, an additional seal is usually provided under the cap, often in the form of a stopper or silicone stopper 11. At the end where the pigment core 8 protrudes out from the casing 2, the finished pencil 1 is generally kept fresh by means of a cap 12 that is placed onto it. The very smooth and scratch-resistant outer surface that is achieved according to the present disclosure fosters the ability of the cap 10 to be slid on in a good and reliable way. The surface achieved according to the present disclosure is so scratch resistant that even after removing and replacing the cap 10 thirty times, no dulling of the surface over which the cap 10 travels occurs that is visible to the naked eye due to micro-scratches and the like extending in the direction of the longitudinal axis of the pencil. The cap 10 is embodied so that it is slightly undersized, i.e. with a slightly smaller inner diameter compared to the outer diameter of the casing 2. The cap 10 that is produced in this way can be slid onto the surface of the casing 2, which is achieved according to the present disclosure, in a suction-inducing fashion and because of its smooth property, can also be pulled off from it again (no stick/slip).

CONCLUDING GENERAL REMARKS

(52) Independent protection, possibly also enhanced with other features from the above description and/or the already existing claims, is claimed for a pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic and that features the fact that after the outer circumference surface is cut into in such a way that a shaving protrudes from the outer circumference, it is possible to peel a skin off the surface of the casing by pulling on the shaving with the unaided hand.

(53) Independent protection, possibly also enhanced with other features from the above description and/or the already existing claims, is claimed for a pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic and the pencil features the fact that its casing has a structure composed of two layers that can be separated from each other by hand and preferably, the one of these two layers that is closer to the surface is thinner.

(54) Independent protection, possibly also enhanced with other features from the above description, is claimed for a pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic, and which pencil features the fact that its casing, viewed in the radial direction, has an outer enrichment zone with a higher concentration of the first plastic than in the middle region.

(55) In this regard, it should be noted that the formation of an inner enrichment zone, possibly through a suitable temperature control at the inner circumference of the casing can be achieved. In instances in which this claim is in force, the above statements apply analogously and only certain limitations, which are based in the inner enrichment zone (which is not present or is purely optional in this variant), are omitted.

(56) Independent protection, possibly also enhanced with other features from the above description and/or the already existing claims, is claimed for a pencil for applying a coloring and/or cosmetic substance, having a pigment core composed of the substance that is to be applied and a one-piece injection-molded casing encompassing the pigment core that is composed of a thermoplastic material that consists of a mix of a first plastic and a second plastic, and which pencil features the fact that its casing, viewed in the radial direction, has an inner enrichment zone with a higher concentration of the first plastic than in the middle region.

(57) In this regard, it should be noted that the formation of an outer enrichment zone, possibly through a suitable temperature control at the outer circumference of the casing can be achieved; the thermal energy that is no longer needed after the injection into the cavity is then removed from the plastic compound of casing essentially via its inner circumference surface. In instances in which this claim is in force, the above statements apply analogously and only certain limitations, which are based in the outer enrichment zone (which is not present or is purely optional in this variant), are omitted.

REFERENCE NUMERAL LIST

(58) 1 pencil 2 casing 3 cross-section of the casing 4 outer circumference 5 inner circumference 6 outer enrichment zone 7 inner enrichment zone 8 pigment core 9 seat 10 closing cap 11 silicone stopper 12 cone 100 measurement point 1 200 measurement point 2 L longitudinal axis of the pencil and its casing S shaving D thickness of the skin A detachment length Pi cone angle