US Patent 6,106,848: Scope of Claims and US Landscape
US Patent 6,106,848 is directed to a topically applicable oil-in-water (O/W) emulsion with intermediate viscosity (3 to 10 Pa·s), stabilized by an anionic amphiphilic polymer emulsifier that produces the claimed viscosity in the absence of another emulsifying agent. The formulation also requires a high level of glycol (30 to 50 wt%), optionally up to 5 wt% thickener/gelling agents, and a broad menu of biologically active agents. Key claim coverage is driven by (i) rheology, (ii) polymer chemistry and composition, and (iii) functional behavior of the polymer emulsifier.
What is the core claim scope (what the patent actually covers)?
Claim 1 sets the technical center of gravity
Independent claim 1 defines the invention as:
- A stable topical O/W emulsion for skin.
- Emulsion viscosity is intermediate:
- 3 to 10 Pa·s (3,000 to 10,000 cP)
- measured on Brookfield LVDV II+, paddle No. 4
- 30 rpm for 30 seconds
- at 25°C ± 3°C.
- Composition requirements:
- (a) Glycol: 30 to 50 wt% of at least one glycol
- (b) Emulsifying agent: at least one emulsifying agent comprising an anionic amphiphilic polymer
- (c) Biologically active agent: at least one biologically active agent
- Polymer functional constraint:
- the anionic amphiphilic polymer is present at an amount such that in the absence of another emulsifying agent it results in an emulsion having intermediate viscosity (3 to 10 Pa·s).
This is not a generic “skin cream” claim. It is a tight formulation claim anchored to:
- O/W emulsion type
- rheology window under a defined instrument/method
- glycol load
- anionic amphiphilic polymer acting as emulsifier with viscosity-generating function
- presence of a biologically active agent.
Dependent claims expand constraints and narrow chemistry
Claims 2 to 20 layer on:
- optional thickener/gelling agents
- pH windows
- polymer crosslinking
- polymer comonomer identity (C10–C30 alkyl ester comonomers)
- crosslinking comonomer identity (non-conjugated polyolefinically unsaturated comonomers, including polyallyl ether)
- specific polymer unit composition ranges for acrylic/acrylate and crosslinking comonomer.
How does claim scope split across formulation, polymer chemistry, and measurement?
A. Formulation boundaries
The claims tie emulsion behavior and composition:
| Variable |
Claim coverage (wt% / units) |
Notes |
| Glycol content |
30 to 50 wt% |
Core requirement (a) |
| Oily phase |
5 to 50 wt% |
Claim 17 |
| Aqueous phase |
10 to 70 wt% |
Claim 18 |
| Thickener/gelling agent |
up to 5 wt% |
Claim 2 |
| Emulsifying agent (b) level |
up to 1 wt% |
Claim 11 |
| Emulsifying agent level range |
0.2 to 0.4 wt% |
Claim 12 |
| pH |
5 to 7 |
Claim 3 |
| pH narrower |
5.5 to 6.5 |
Claim 4 |
| Biologically active agent load |
0.0001 to 20 wt% |
Claim 16 |
B. Polymer emulsifier identity and behavior
The polymer is required to be:
- anionic amphiphilic
- an emulsifying agent
- with a functional role: intermediate viscosity even without another emulsifying agent.
Dependent claims specify polymer architecture:
- crosslinked anionic amphiphilic polymer (Claim 5)
- polymer is a copolymerizate of:
- olefinically unsaturated carboxylic comonomers
- and C10–C30 alkyl ester comonomers (Claim 6)
- crosslinked using:
- olefinically unsaturated and non-conjugated polyolefinically unsaturated comonomers (Claim 7)
- with a non-conjugated polyolefinically unsaturated comonomer including polyallyl ether (Claim 8).
C. Polymer unit composition constraints (hard numeric anchors)
Two mutually consistent composition windows appear in dependent claims:
| Claim |
Acrylic structural units (wt%) |
Acrylate structural units (wt%) |
Crosslinking comonomer (wt%) |
| Claim 9 |
95 to 60 |
4 to 40 |
0.1 to 6 |
| Claim 10 |
98 to 96 |
1 to 4 |
0.1 to 0.6 |
These claims impose the largest risk of “design around” by altering monomer ratios or crosslink density outside the numeric windows.
What is the biologically active agent coverage?
Claim 15 keeps the active-agent scope broad. The biologically active agent (c) may be selected from a long list including:
- agents modulating skin differentiation, proliferation, and pigmentation
- antibacterial, antiparasitic, antifungal
- steroidal and non-steroidal anti-inflammatory
- anaesthetic, antipruritic
- antiviral
- keratolytic
- anti-free radical
- antiseborrhoeic / antidandruff
- anti-acne
- antimetabolite
- hair loss combat agent
- antiseptic
Claim 16 then sets an allowable range:
- 0.0001 to 20 wt% of biologically active agent relative to emulsion weight.
From a freedom-to-operate perspective, the presence of a biologically active agent is not a limiter that disappears if actives change; it is an eligibility requirement that remains satisfied even by low-dose actives.
Where is the “rheology + emulsifier” choke point?
Claim 1 contains a functional limitation that is often the most enforceable element:
- The amount of the anionic amphiphilic polymer must be such that without another emulsifying agent the emulsion still hits the viscosity range.
This creates two distinct infringement scenarios:
- Accused product matches all numerical ranges and uses the polymer as the effective emulsifier and viscosity driver.
- Even if an accused formulation includes an additional emulsifier, infringement can still occur if the polymer’s amount meets the functional viscosity requirement in its absence.
Designing around requires breaking at least one of:
- glycol wt% window,
- polymer type/behavior,
- viscosity window measured with the specified Brookfield method,
- pH window (if asserted with dependent claims),
- crosslinking and comonomer structure windows (if asserted with dependent claims),
- polymer unit composition ranges (if asserted with dependent claims).
How do claims 2 to 20 layer practical narrowing?
Claims that narrow product feel and stability parameters
- Claim 2: up to 5% thickener/gelling agent
- Claims 3-4: pH 5 to 7, or 5.5 to 6.5
- Claims 17-18: oily and aqueous phase proportions
These are useful to invalidate or distinguish an accused product even if the polymer and glycol are present.
Claims that narrow polymer chemistry (high precision)
- Claims 5-8: crosslinked anionic amphiphilic polymer and crosslink comonomer definitions, including polyallyl ether
- Claims 9-10: polymer unit composition and crosslink comonomer wt% ranges
If an accused formulation uses a different emulsifier polymer (different monomer types, different crosslinker chemistry, non-crosslinked or different acrylate/acrylic distribution), it can avoid dependent-claim coverage even if claim 1 is approached.
Claim chart style mapping: what elements must be present for infringement?
Element-by-element for Claim 1
A product must satisfy all the following:
- Stable topical O/W emulsion applied to skin.
- Intermediate viscosity:
- 3 to 10 Pa·s
- Brookfield LVDV II+ paddle No. 4
- 30 rpm 30 seconds
- 25°C ± 3°C.
- Contains:
- 30 to 50 wt% glycol (selected from: propylene glycol, dipropylene glycol, propylene glycol dipelargonate, lauroglycol, ethoxydiglycol) per Claim 13 or possibly broader per Claim 1
- emulsifying agent comprising an anionic amphiphilic polymer
- at least one biologically active agent.
- Functional polymer requirement:
- in the absence of another emulsifying agent, the polymer amount still yields intermediate viscosity.
What is the likely US patent landscape around this claim set?
Landscape drivers
Even without asserting specific citations for other patents, the landscape logic is determined by the claim architecture:
- O/W emulsions for dermatology with glycols and actives are common.
- Polycarboxylate/acrylate amphiphilic polymers used as emulsifiers and thickeners are also common.
- The differentiator is the combination of:
- high glycol load (30 to 50%)
- specific viscosity window measured by Brookfield LVDV II+ paddle 4 at 30 rpm
- functional limitation tying polymer amount to viscosity in the absence of another emulsifier
- crosslinked polymer and specific comonomer families (C10–C30 alkyl ester; non-conjugated polyolefinically unsaturated crosslinker such as polyallyl ether)
- narrow acrylic/acrylate/crosslinker unit distribution windows.
Practical implication for competitive filings
Products that differ only in the active ingredient but keep:
- the same glycol range,
- the same polymer architecture, and
- rheology window,
remain in the core risk zone.
Competitive filings that most effectively reduce risk typically diverge in at least two axes:
- replace the polymer emulsifier with a different emulsifier class (non-anionic amphiphilic or non-crosslinked, or different monomer system),
- move out of the Brookfield viscosity window (or use a different formulation strategy so polymer alone does not yield intermediate viscosity),
- move glycol concentration below 30% or above 50%,
- avoid the dependent polymer composition and crosslinking structure windows.
Key “scope traps” that can expand infringement exposure
- Presence of any biologically active agent
- If the product is marketed as therapeutic or contains actives meeting the list, claim 1 eligibility is often satisfied.
- Polymer functional limitation
- The “in absence of another emulsifying agent” language can force analysis of whether polymer alone produces the intermediate viscosity.
- Broad glycol list but fixed wt%
- Many dermatologic formulations contain glycols but not at 30 to 50 wt%.
- Measurement method is specific
- Products that hit similar viscosity by another method may still infringe if they match the stated Brookfield method and operating conditions.
What does the dependent-claims ladder do in enforcement?
Dependent claims can create incremental settlement leverage because each narrows to particular polymer compositions and pH/thickener conditions:
- If the accused product matches only the general polymer class and glycol range, claim 1 is still the main battleground.
- If the accused product also matches crosslinking and comonomer identity, claims 5 through 8 become relevant.
- If unit composition falls into the numeric windows, claims 9 and 10 become relevant.
- If pH is in range and thickener level fits, claims 2 through 4 can be added to strengthen infringement positions.
Key Takeaways
- US 6,106,848 claims a specific dermatologic O/W emulsion platform: 30 to 50 wt% glycol, intermediate Brookfield viscosity (3 to 10 Pa·s), and anionic amphiphilic polymer emulsifier that yields that viscosity without another emulsifier, plus a biologically active agent.
- The most enforceable technical discriminator is the rheology window combined with polymer functional behavior.
- Dependent claims significantly tighten infringement through:
- crosslinked amphiphilic polymer chemistry (olefinically unsaturated carboxylic plus C10–C30 alkyl ester comonomers; non-conjugated polyolefinically unsaturated crosslinker such as polyallyl ether),
- acrylic/acrylate/crosslinker unit distribution (Claims 9-10),
- pH windows and optional thickener load.
- Competitive design around typically must change at least two axes: glycol concentration, polymer architecture/function, and Brookfield-measured viscosity behavior.
FAQs
1) Does claim 1 require a specific glycol identity?
Claim 1 requires “at least one glycol” at 30 to 50 wt%. A specific glycol list appears in dependent Claim 13, but the independent claim is not restricted to that list.
2) Is the viscosity requirement a qualitative range or a measured parameter?
It is a quantified range (3 to 10 Pa·s) with a defined Brookfield instrument, paddle, speed, dwell time, and temperature.
3) What is the role of the anionic amphiphilic polymer in claim 1?
It is the emulsifying agent and must be present at an amount that produces intermediate viscosity even without another emulsifying agent.
4) How broadly does the patent cover active ingredients?
Claim 15 lists multiple therapeutic categories (anti-infectives, anti-inflammatory, keratolytics, etc.) and Claim 16 permits actives from 0.0001 to 20 wt%.
5) Which dependent claims most constrain polymer chemistry?
Claims 5 through 10: crosslinking, comonomer types (including C10–C30 alkyl ester), crosslinker family (including polyallyl ether), and the numeric unit composition windows.
References
- US Patent 6,106,848 (claims as provided in prompt).
