Pencil lead with polyhydroxybutyric acid binder and pencil with the lead
Patent Information
- Application Number
- EP2023754141
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-08-05
- Filing Date
- 2023-08-02
- Publication Date
- 2025-06-11
AI Technical Summary
Conventional pen leads based on crude oil-derived polymers are non-renewable, costly, and strain natural resources, while biodegradable alternatives face challenges in maintaining performance characteristics like sharpness, coloring strength, and erasability.
A pen lead composition using polyhydroxybutyric acid as a binder, combined with fillers, waxes, and additives, which includes copolymers like poly(3-hydroxyvaleric acid) and polylactic acid, to create a biodegradable and environmentally friendly alternative that maintains performance while reducing reliance on fossil fuels.
The use of polyhydroxybutyric acid and its copolymers in pen leads results in a high-quality, biodegradable writing instrument that optimizes mechanical properties, coloring, and erasability without compromising on sharpness or opacity, while being environmentally friendly and reducing production costs.
Abstract
Description
[0001] Pencil lead with polyhydroxybutyric acid as a binder and pencil with the pencil lead
[0002] The invention relates to a pencil lead for writing, drawing, painting and / or cosmetic pencils based on biodegradable binders with the features of claim 1. The invention also relates to a pencil with the pencil lead.
[0003] Pencil leads for writing, drawing, painting and / or cosmetics containing polymers produced from crude oil are known.
[0004] EP 2644407 A1 describes polymer-bonded expanded leads containing biodegradable binders and graphite as a colorant. The strength and coverage of such leads can be optimized, particularly in pencil leads.
[0005] Furthermore, DE 19855325 A1 describes a coating for colored or lead leads based on cellulose and biodegradable polymers. A variety of biopolymers for coating lead leads are described, but no indication is given of how a lead could be manufactured using such biopolymers.
[0006] A polymer-bonded dye and graphite lead is known from WO 2010 / 006742 A1. Such leads contain a polymer binder, wax, palm oil, and fillers. Most polymer leads are based on crude oil products and are therefore directly dependent on the price and availability of oil. Furthermore, leads manufactured from crude oil-derived polymers consume naturally occurring, non-renewable resources.
[0007] Furthermore, polymer-bonded dye and graphite leads are known from US 2988784 A. Such leads contain a polymeric binder based on cellulose esters, particularly cellulose acetate, wax, and filler. Although these leads are made from a natural raw material and can therefore be completely mined, they consist largely of the naturally occurring raw material wood. Due to the high demand for wood, however, it is becoming increasingly difficult and expensive to acquire high-quality wood. Furthermore, the dwindling supply of natural wood is being severely strained by the production of pencils with cellulose esters.
[0008] The object of the invention is therefore to develop a pencil lead and a pen with the pencil lead for writing, drawing and / or painting, whereby the pencil lead forms an environmentally friendly alternative without losing the primary properties, for example the sharpenability, the coloring, the strength, the opacity of the stroke and / or the erasability of the pencil lead.
[0009] The subject matter of the invention is a pencil lead having the features of claim 1 and a pencil having the features of claim 7. Preferred or advantageous embodiments of the invention emerge from the subclaims and the following description.
[0010] The invention relates to a pencil lead for writing pens, drawing pencils, colored pencils, and / or cosmetic pencils, consisting of filler, colorant, binder, and other additives. The pencil lead can be designed as a colored pencil lead or as a pencil lead.
[0011] Pencil leads for writing, drawing, painting, and / or cosmetic use are understood to mean, in particular, pencil leads that are firmly embedded in a shaft material, e.g., wood, or extruded mixtures, e.g., a polymer mixture, and which are sharpenable. Alternatively, pencil leads can be slidably mounted in a rigid casing. Examples of this are wood-cased pencils and pencil leads for mechanical pencils, e.g., so-called mechanical pencils or drop-action pencils. The pencil leads in particular have outer diameters in the range of approximately 0.3 mm to 6 mm. According to the invention, the pencil lead has the following components, based on the pencil lead, in particular on the total weight of the pencil lead:
[0012] 5 to 65 wt.% binder comprising polyhydroxybutyric acid and / or a copolymer with polyhydroxybutyric acid as the first polymer and a second polymer,
[0013] 33 to 85 wt.% filler with colorant,
[0014] 2 to 33% by weight of wax or waxes,
[0015] 0 to 1 wt.% other additives such as stabilizers, lubricants.
[0016] According to the invention, the binder comprises polyhydroxybutyric acid. Polyhydroxybutyric acid is abbreviated as PHB and is registered with the Chemical Abstracts Service under the number CAS: 26063-00-3. Depending on the number of monomers in the polymer, the properties of PHB as a polymer can vary somewhat. Polyhydroxybutyric acid has thermoplastic properties and is biodegradable.
[0017] Alternatively or additionally, the binder comprises a copolymer with polyhydroxybutyric acid as the first polymer. A copolymer is understood to be a polymer composed of, in particular, exactly two polymers. The polymers of the copolymer are chemically bonded. In the copolymer based on polyhydroxybutyric acid, the first polymer is polyhydroxybutyric acid. The second polymer is selected according to the required properties. Preferably, the second polymer is bio-based and / or biodegradable. Particularly preferably, the second polymer is more flexible than polyhydroxybutyric acid.
[0018] It has surprisingly been shown that a high-quality pencil lead can be produced using polyhydroxybutyric acid and / or a copolymer comprising polyhydroxybutyric acid as the first polymer as a binder, with polyhydroxybutyric acid being an environmentally friendly alternative due to its biodegradability. In one embodiment, the binder comprises only polyhydroxybutyric acid. In another embodiment, the binder comprises only a copolymer with polyhydroxybutyric acid as the first polymer and a second polymer. In another embodiment, the binder comprises a mixture of polyhydroxybutyric acid and a copolymer with polyhydroxybutyric acid as the first polymer and the second polymer.
[0019] In particular, the filler is selected from a group comprising hexagonal boron nitride, phyllosilicates, chalk, barite, colored pigments and / or achromatic pigments, or mixtures thereof. This allows for the production of a pencil lead that is optimized in terms of cost and mechanical properties.
[0020] The filler may additionally comprise graphite and / or carbon black, which simultaneously act as colorants. For black pencil leads, graphite and / or carbon black are preferably selected individually or as a mixture thereof as filler and colorant. In particular, black pencil leads are referred to as pencil leads or graphite leads.
[0021] Colorants are used to color the pencil lead, creating a colored abrasion when writing. The colorant is typically selected from a group including titanium dioxide, zinc sulfide, colored pigments, carbon black, graphite, and / or mixtures thereof. This allows the color of the pencil lead to be selected.
[0022] Other additives include stabilizers and lubricants.
[0023] Stabilizers are added to the pencil lead to slow the polymer's aging processes. Exposure to heat, light, ozone, and oxygen can lead to aging processes, which become apparent in the deterioration of the pencil's properties, for example, as color changes.
[0024] In particular, lubricants are added to the lead of mechanical or drop-action pencils to prevent the lead from becoming stuck in the barrel. Furthermore, lubricants facilitate pencil movement across the paper and improve the transfer of the coloring agents from the lead to the writing surface, such as blackboards, paper, concrete, asphalt, or skin. The lubricant contains palm oil.
[0025] In one embodiment, the copolymer has a weight ratio of polyhydroxybutyric acid as the first polymer and the second polymer in the range of 1:10 to 10:1, preferably in the range of 5:10 to 10:5, in particular based on the total weight of the binder.
[0026] In another embodiment, the second polymer of the copolymer comprises poly(3-hydroxyvaleric acid). Poly(3-hydroxyvaleric acid) is specifically a name for poly(3-hydroxybutyrate-co-3-hydroxyvalerate) and / or known as PHV (CAS: 83120-66-5). It is bio-based and biodegradable.
[0027] In particular, the binder comprises only copolymers of polyhydroxybutyric acid as the first polymer with poly(3-hydroxyvaleric acid) as the second polymer with a weight ratio in the range of 1:10 to 10:1, preferably in the range of 5:10 to 10:5, in particular based on the total weight of the binder.
[0028] In particular, the binder comprises a mixture of polyhydroxybutyric acid, poly(3-hydroxyvaleric acid), and / or polylactic acid. The binder preferably consists of the mixture. A mixture of polymers is referred to as a blend.
[0029] PLA is the abbreviation for polylactic acid, which can be referred to specifically as polylactide and / or polylactic acid. PLA is also registered with the Chemical Abstracts Service under the number CAS: 9051-89-2. Depending on the number of monomers in the polymer, the properties of PLA as a polymer can vary slightly.
[0030] PLA is a thermoplastic. PLA has the advantage of being bio-based, significantly reducing or completely eliminating the use of petroleum-based raw materials in the pen. PLA, for example, is derived from corn and, as a synthetic polymer, belongs to the polyester family. Thus, pure PLA is preferably made from renewable resources and is not based on fossil fuels such as petroleum.
[0031] In particular, the binder comprises a mixture of
[0032] Polyhydroxybutyric acid, poly(3-hydroxyvaleric acid) and polylactic acid. In particular, the binder comprises a mixture of
[0033] Polyhydroxybutyric acid and poly(3-hydroxyvaleric acid). In particular, the binder comprises a mixture of poly(3-hydroxyvaleric acid) and polylactic acid. In particular, the binder comprises a mixture of polyhydroxybutyric acid and polylactic acid.
[0034] This makes it possible to select properties such as abrasion and mechanical strength for biodegradable binders.
[0035] Other copolymers based on polyhydroxybutyric acid are possible, expanding the range of properties. This allows for adjustment of mechanical properties—especially sharpenability, color, strength, opacity, erasability, etc.—as well as manufacturing costs.
[0036] In a preferred embodiment, the pencil lead has a binder content preferably in the range of 8 to 50 wt.%, preferably in the range of 15 to 27 wt.%, based on the total mass of the pencil lead. This has the advantage that the binder content can optimize production costs while simultaneously providing mechanical properties in the pencil lead.
[0037] In a further embodiment, the pencil lead comprises at least one wax or a mixture of waxes as a wax mixture. The at least one wax is selected from a group comprising fatty acids, stearates, montan wax, amide wax, carnauba waxes, beeswax, paraffin, polyolefin waxes, polyethylene wax, polyethylene vinyl acetate waxes, and mixtures thereof. The wax also comprises further additives. Several different waxes can be used as a wax mixture.
[0038] Preferably, the wax comprises a mixture of polyethylene wax and / or polyethylene vinyl acetate wax.
[0039] Preferably, the at least one wax is selected from the group comprising calcium stearate and / or ethylene bisstearamide (EBS). Ethylene bis(stearamide) is, in particular, a name for distearylethylenediamide and / or is known as EBS (in particular CAS: 110-30-5). Calcium stearate (CAS: 1592-23-0) is also part of the European list of food additives as E470a. In particular, the wax additionally comprises Biomers from Deurex.
[0040] In a further embodiment, the pencil lead has a colorant content in the range of 0 to 10 wt.% based on the pencil lead.
[0041] In a further embodiment, the pencil lead has the following components related to the pencil lead, in particular to the total weight of the pencil lead:
[0042] 8 to 50 wt.% binder comprising polyhydroxybutyric acid and / or a copolymer with polyhydroxybutyric acid as the first polymer and a second polymer,
[0043] 40 to 80 wt.% filler with colorant,
[0044] 5 to 28 wt% wax or waxes,
[0045] 0 to 1 wt.% other additives such as stabilizers, lubricants.
[0046] In particular, when the pencil lead is used in a pen with a shaft, an adhesion promoter is used. The adhesion promoter has the advantage that the pencil lead is arranged in the shaft in a way that prevents it from shifting. This means that the pencil lead does not shift into the shaft when light pressure is applied while writing. A further subject matter of the invention is a pen with the pencil lead as described above. The pen is designed in particular as a writing pen, drawing pen, painting pen and / or cosmetic pencil. The pen has the pencil lead and a shaft, wherein the shaft preferably surrounds the pencil lead concentrically and / or coaxially. The pencil lead is preferably arranged with the shaft in a way that is fixed and / or immovable relative to one another. In particular, the pencil lead is permanently and irremovably fixed in the shaft and / or cannot be removed without damage. Alternatively, the pencil lead is mounted so that it can be moved within the pen.For example, the pen is designed as a mechanical pencil or a drop pencil.
[0047] Further features, advantages and effects of the invention will become apparent from the following description of preferred embodiments of the invention:
[0048] The pencil lead according to the invention is preferably produced after mixing and granulating the components of the pencil lead in an extrusion process or coextrusion process as a strand of a pencil lead at approximately 150 to 200°C.
[0049] The shape of the lead's cross-sectional area is set in the extrusion head. When producing leads for drop-action pencils, the lead strand is additionally cut to a specific length. For lead for shaft-type pencils, the lead is coated with a shaft material as one of the subsequent process steps.
[0050] Example compositions for pencil leads are shown below.
[0051] Example 1 : Pen refill with the following components:
[0052] 17.5 wt.% polyhydroxybutyric acid as binder,
[0053] 67.5 wt% talc and / or kaolin as filler,
[0054] 7 wt.% carbon black as a colorant,
[0055] 3 wt.% polyethylene wax as wax,
[0056] 5% by weight polyethylene vinyl acetate wax as wax. The advantage is the high filler content combined with a biodegradable binder, which allows for the production of a largely biodegradable pencil lead.
[0057] Example 2: Pencil lead as pen lead with the following components:
[0058] 60 wt.% copolymer of polyhydroxybutyric acid and poly(3-hydroxyvaleric acid) in a weight ratio of 2:1, in particular based on the total weight of the binder, preferably corresponds to 40 wt.% polyhydroxybutyric acid and 20 wt.% poly(3-hydroxyvaleric acid) as binder,
[0059] 34 wt.% graphite and carbon black, in particular in a weight ratio of 1 :2 as filler with colorant,
[0060] 2 wt.% polyethylene wax as wax,
[0061] 4 wt% polyethylene vinyl acetate wax as wax.
[0062] The copolymer reduces the proportion of crystalline areas and facilitates the abrasion of the pencil lead and thus writing.
[0063] Example 3: Pen refill with the following components:
[0064] 26 wt.% polyhydroxybutyric acid as a binder,
[0065] 55 wt.% layered silicates as filler,
[0066] 10 wt.% red pigment as colorant,
[0067] 5 wt.% polyethylene wax as wax,
[0068] 3 wt.% polyethylene vinyl acetate wax as wax,
[0069] 1% by weight palm oil as a lubricant.
[0070] Example 4: Pen refill with the following components:
[0071] 7 wt.% poly(3-hydroxyvaleric acid) as binder,
[0072] 81 wt.% graphite as filler,
[0073] 2 wt.% carbon black as a colorant,
[0074] 6 wt.% ethylene bis-stearamide as wax,
[0075] 4% by weight calcium stearate as wax. Example 5: Pencil lead with the following ingredients:
[0076] 40 wt.% copolymer of polyhydroxybutyric acid and poly(3-hydroxyvaleric acid) as binder, in particular in a ratio of 1:4, especially based on the total weight of the binder, preferably corresponds to 8 wt.% polyhydroxybutyric acid and 32 wt.% poly(3-hydroxyvaleric acid),
[0077] 46 wt.% barite as filler,
[0078] 10% by weight yellow pigment as colorant,
[0079] 2 wt.% polyethylene wax as wax,
[0080] 2% w / w calcium stearate as wax.
[0081] Example 6: Pen refill with the following components:
[0082] 16 wt.% mixture or blend of polyhydroxybutyric acid and polylactic acid as binder, in particular in the ratio 3:1, preferably corresponds to 12 wt.% polyhydroxybutyric acid and 4 wt.% polylactic acid,
[0083] 74 wt.% hexagonal boron nitride as filler,
[0084] 5 wt.% carbon black and titanium dioxide pigment as colorant,
[0085] 4 wt.% ethylene bis-stearamide as wax,
[0086] 6 wt% polyethylene vinyl acetate wax as wax.
[0087] Example 7: Pen refill with the following components:
[0088] 26 wt.% mixture or blend of polyhydroxybutyric acid and polylactic acid as binder, in particular in the ratio 27:10, preferably corresponds to 19 wt.% polyhydroxybutyric acid and 7 wt.% polylactic acid,
[0089] 55 wt.% layered silicates as filler,
[0090] 10 wt.% green pigment as colorant,
[0091] 5 wt.% polyethylene wax as wax,
[0092] 3 wt.% polyethylene vinyl acetate wax as wax,
[0093] 1% by weight palm oil as a lubricant.
[0094] These examples can be used to produce pencil leads that contain a biodegradable binder.
Claims
Claims: Pencil lead for writing pens, drawing pencils, painting pencils and / or cosmetic pencils, which comprises binding agents, fillers, colorants and other additives, characterized in that the pencil lead contains the following components: 5 to 65 wt.% binder comprising polyhydroxybutyric acid and / or a copolymer with polyhydroxybutyric acid as the first polymer and a second polymer, 33 to 85 wt.% filler with colorant, 2 to 33% by weight of wax or waxes, 0 to 1 wt. % of other additives such as stabilizers, lubricants. Pencil lead according to claim 1, characterized in that the binder is biodegradable. Pencil lead according to one of the preceding claims 1 or 2, characterized in that the copolymer has a weight ratio of polyhydroxybutyric acid as the first polymer and the second polymer in the range of 1:10 to 10:1, preferably in the range of 5:10 to 10:
5. Pencil lead according to one of the preceding claims, characterized in that the second polymer of the copolymer comprises poly(3-hydroxyvaleric acid). Pencil lead according to one of the preceding claims, characterized in that the copolymer of the binder with polyhydroxybutyric acid and poly(3-hydroxyvaleric acid) as the second polymer has a weight ratio in the range of 1:10 to 10:1, preferably in the range of 5:10 to 10:
5. comprises. Pencil lead according to one of the preceding claims, characterized in that the binder comprises a mixture of polyhydroxybutyric acid, poly(3-hydroxyvaleric acid) and / or polylactic acid. Pencil lead according to one of the preceding claims, characterized in that the pencil lead comprises a binder content in the range of 8 to 50 wt. %, preferably in the range of 15 to 27 wt. %, based on the pencil lead. Pencil lead according to one of the preceding claims, characterized in that the pencil lead comprises a wax content in the range of 2 to 33 wt. %, preferably in the range of 5 to 28 wt. %, based on the pencil lead. Pencil lead according to one of the preceding claims, characterized in that the pencil lead comprises a colorant content in the range of 0 to 10 wt. % based on the pencil lead. Pencil with a pencil lead according to one of the preceding claims.